Electrolux TC6 Specifications

University of Southern Queensland
FACULTY OF ENGINEERING AND SURVEYING
MOBILE MANOEUVRING
ROBOT
A dissertation submitted by
Mr. Matthew Free
in fulfilment of the requirements of
Courses ENG4111 and 4112 Research Project
towards the degree of
Bachelor of Engineering
(Mechatronics)
Submitted: November, 2006
ABSTRACT
Robotic guidance is a large part of many research and design applications. It is being
used more frequently in everyday lifestyles such as vacuum cleaners and lawn mowers,
and is slowly being introduced into the automobile industry.
The need for this technology is growing evermore and different aspects and methods are
being implemented, from various sensor types to camera machine vision.
This
dissertation is compiled to explore the use of one of these technologies implemented
into a small unit.
This dissertation develops and analyses the use of Mechatronic technology in the use of
household applications.
The overall objective of this project is to implement a
microprocessor based controller in a small mobile robot to achieve straight line driving
with implemented obstacle avoidance.
i
University of Southern Queensland
FACULTY OF ENGINEERING AND SURVEYING
ENG4111 & ENG 4112 Research Project
Limitations of Use
The Council of the University of Southern Queensland, its Faculty of Engineering and
Surveying, and the staff of the University of Southern Queensland, do not accept any
responsibility for the truth, accuracy or completeness of material contained within or
associated with this dissertation.
Persons using all or any part of this material do so at their own risk, and not at the risk
of the Council of the University of Southern Queensland, its Faculty of Engineering and
Surveying or the staff of the University of Southern Queensland.
This dissertation reports an educational exercise and has no purpose or validity beyond
this exercise. The sole purpose of the course pair entitled “Research Project” is to
contribute to the overall education within the students chosen degree program. This
document, the associated hardware, software, drawings, and other material set out in the
associated appendices should not be used for any other purpose: if they are so used, it is
entirely at the risk of the user.
Prof R Smith
Dean
Faculty of Engineering and Surveying
ii
Certification
I certify that the ideas, designs and experimental work, results analysis and conclusions
set out in this dissertation are entirely my own efforts, except where otherwise indicated
and acknowledged.
I further certify that the work is original and has not been previously submitted for
assessment in any other course or institution, except where specifically stated.
Matthew Phillip Free
Student Number: 0050009628
____________________________
Signature
____________________________
Date
iii
ACKNOWLEDGEMENTS
This research was carried out under the principal supervision of Mark Phythian. Many
thanks are due for his expertise and advice in the area surrounding the Mobile
Manoeuvring Robot
Assistance was also obtained from Mr. Terry Byrnes. Many thanks also to his expertise
and advice.
The University of Southern Queensland supplied vital components for the construction
of the Mobile Manoeuvring Robot. Many thanks for the use of these components.
Appreciation is also due to Garth and Diana Free for the use of manufacturing tools and
materials.
iv
TABLE OF CONTENTS
Contents
Page
ABSTRACT
i
DISCLAIMER PAGE
ii
CANDIDATES CERTIFICATION
iii
ACKNOWLEDGEMENTS
iv
LIST OF FIGURES
viii
LIST OF TABLES
ix
LIST OF APPENDICES
x
NOMENCLATURE
xi
1. CHAPTER 1 – Introduction
1
1.1.
Outline of the study
1
1.2.
The problem
1
1.2.1.
Project Goals
2
1.2.2.
Performance Guidelines
3
1.3.
Research objectives
3
1.4.
Conclusions: Chapter 1
4
2. CHAPTER 2 – Literature Review
5
2.1.
Introduction
5
2.2.
The Need for Autonomous Applications
7
2.3.
Sensing Distances in Applications
8
2.4.
Object Avoidance
9
2.5.
Dual Motor Drive Systems
11
2.6.
Consequential effects and outcomes
12
2.7.
Summary: Chapter 2
14
3. CHAPTER 3 – Research Design and Methodology
3.1.
Safety issues
15
15
3.1.1.
Mechanical Safety Issues
15
3.1.2.
During The Electrical System Creation
17
v
3.1.3.
During the Testing Procedure
17
3.2.
Resource Requirements
17
3.3.
Sustainability
18
3.4.
Methodology
19
3.5.
Justification of Methodology
20
4. CHAPTER 4 – Data Analysis
21
4.1.
Initial Design
21
4.2.
Second Prototype
22
4.3.
Odometer sensors and interrupt control
23
4.3.1.
Building the odometer sensors
23
4.3.2.
Using interrupts to count odometer readings
24
4.4.
H Bridge Motor Control
27
4.5.
Infrared Distance Sensors
29
Requirements and Availability
29
4.5.2.
Choice of Sensor
31
4.5.3.
Design and construction of IR Sensor
31
4.6.
4.5.1.
The Software
39
4.6.1.
Address Definition
41
4.6.2.
Variable Definition
42
4.6.3.
Main Program
42
4.6.4.
DRFWD Drive Forward Subroutine
43
4.6.5.
Turning Subroutines
44
4.6.6.
Delay
46
4.6.7.
COMP Compare subroutine
47
4.6.8.
KWGISR Key Wake up Port G
48
4.6.9.
IRQISR IRQ Interrupt Service Routine
49
4.6.10.
Initialisation of Ports and Interrupts
50
4.6.11.
Serial Port Communications
52
5. CHAPTER 5 – Performance and Data Analysis
54
5.1.
Sensor Performance
54
5.2.
Mechanical Performance
57
5.3.
Software Performance
58
vi
5.4.
Overall Performance
60
5.5.
Conclusions
61
6. CHAPTER 6 Debugging Module
62
6.1.
Microcontroller Not working
62
6.2.
Motors Not Turning
62
6.3.
Not stopping for Objects
63
6.4.
Not driving in a Straight Line
64
6.5.
Stopping for Objects but irregular behaviour
64
7. CHAPTER 7 Future Work
7.1.
65
Hardware
7.1.1.
Chassis Design
65
7.1.2.
Sensor Design
65
7.1.3.
Power Source Design
66
7.1.4.
Software Design
66
8. CHAPTER 8 Conclusions
67
APPENDICES
69
REFERENCES
97
vii
LIST OF FIGURES
Number
Title
Page
Figure 2.1:
Army Bomb Deployment
6
Figure 2.2:
Bomb Disposal Robot
6
Figure 2.3:
Increasing technologies
7
Figure 4.1:
Initial Chassis Prototype
21
Figure 4.2:
Second Chassis Prototype
22
Figure 4.3:
Motor setup
23
Figure 4.4:
Chassis design
23
Figure 4.5:
Odometer Sensor
23
Figure 4.6:
Single hole odometer sensor
24
Figure 4.7:
Odometer Sensor Circuitry
24
Figure 4.8:
4013 Flip-Flop configuration
25
Figure 4.9:
Basic H Bridge Operation
27
Figure 4.10:
Sensor Distance Requirements
30
Figure 4.11:
555 Timer Pulsing Sensor Light
32
Figure 4.12:
PCB inside LED Torch
33
Figure 4.13:
LED Torch Complete With Wires
33
Figure 4.14:
Power Supply Filter for Transmitter
34
Figure 4.15:
Position of Sensor Components
36
Figure 4.16:
Sensor mounting on the Robot
37
Figure 4.17:
Data flow for software
40
Figure 5.1:
Sensor spectrum
56
Figure 5.2:
Layered approach to robot design.
58
Figure 5.3:
Straight line testing
59
Figure 5.4:
Results of straight line test
59
Figure 6.1:
Showing IR LED status
63
Figure 8.1:
Working Prototype of Mobile Manoeuvring Robot
68
viii
LIST OF TABLES
Number
Title
Page
Table 3.1:
Cutting aluminium safety
15
Table 3.2:
Grinding and die grinding safety
16
Table 3.3:
Drilling safety
16
Table 3.4:
Lathe safety
16
Table 3.5:
Painting Safety
17
Table 3.6:
soldering safety
17
Table 3.7:
Testing safety
17
Table 3.8:
Mechanical resources
17
Table 3.9:
Electronic Resources
17
Table 5.1:
Sensor range
55
ix
LIST OF APPENDICES
Number
Title
Page
A
Project Specification
70
B
Software Listing
71
C
Software Design Procedure
85
D
Component Data Sheets
91
x
NOMENCLATURE AND ACRONYMS
The following abbreviations have been used throughout the text and bibliography:-
CRO – Cathode Ray Oscilloscope
DSE – Dick Smith Electronics Australia
IC – Integrated Circuit
IR – Infrared or Infrared Light
LED – light emitting diode
PCB – Printed Circuit Board
PWM – Pulse Width Modulation
USQ – University of Southern Queensland (Toowoomba Campus)
xi
CHAPTER 1
INTRODUCTION
1.1 Outline of the study
The final objective of this project is to implement a successful electronic system into a
small mechanical unit in an attempt to make it travel throughout an area whilst avoiding
obstacles to evade collisions. In this case the solution will come from the selection of a
suitable microcontroller, drive system and sensors.
Further work may be completed to make this device actually perform a practical task
such as object retrieval; however this is not essential to the outcomes of this project.
The project objective will be satisfied if the software and hardware configuration is able
to control the vehicle within an indoor environment whilst avoiding collision with
obstacles.
1.2 The problem
The overall project objective is stated above as “to implement a microprocessor based
controller in a small mobile robot to achieve straight line driving with implemented
obstacle avoidance.”
The project objective will be satisfied if the software and hardware configuration is able
to control the vehicle within an indoor environment whilst avoiding collision with
obstacles.
This means the unit will have such features as odometer counters for each wheel to aid
in turning and driving in straight lines and hopefully record where it is in regards to its
starting position. At least three sensors will be used to ‘read’ the path to the front and
both sides of the unit. This will be necessary in the path tracking of the unit, i.e.
deciding on which way to turn in an attempt to avoid collision.
1
1.2.1 Project Goals
In order to reach the overall objective of this project it is necessary to consider a set of
guidelines or a set of project goals to direct the progress of achievement. They are set to
be a set of open statements allowing a lot of movement and flexibility within them but
to globally control the direction and outcome of the project.
By pursuing the following goals the project objective should be reached satisfactorily.
1. Define a guideline to assess the performance of the robot to the specifications of
the project objective.
2. Build a prototype that is practical to the objective
3. Research the background behind obstacle avoidance and other attempts to
achieve similar tasks.
4. Research microcontrollers and sensors to acquire the most practical
configuration as to meet the objective.
5. Define an initial design of the configuration and code to be implemented.
6. Construct initial design
7. Test and analyse the results in accordance to the performance guidelines.
8. Re evaluate the design as required to achieve the project objective.
As time permits the following steps will be undertaken to improve on the robot and
extend the project outcomes.
o Define a new performance guideline for the practical task completion
o Research more methodology if required
o Re design and construct the robot to achieve the new objective.
o Test and analyse the results in accordance to the new performance guidelines
o Evaluate and change the design as required to achieve new objectives.
2
1.2.2 Performance Guidelines
The first project goal is to define a guideline to assess the performance of the robot to
the specifications of the project objective.
For this project to be successful in accordance with the project objective, it is required
that the robot perform to the following criteria.
•
Travel in a straight line when in a clear area with no manual assistance.
•
Stop before colliding with any obstacles that are in the path
•
“Decide” which way is more practical to turn and do so.
•
Continue on its path in a straight line.
If the robot adheres to this criterion it will be able to drive continuously, avoiding
collision on a random path.
1.3 Research objectives
The research in this project will basically revolve around similar projects and concepts
developed to achieve similar tasks. The methods that have been used in various areas
will be evaluated in comparison with each other and the superior designs analysed and
modified to enable a suitable proposal for the manoeuvring robot.
The main research has been compiled into a literature review and is detailed in chapter 2
‘Literature Review’.
3
1.4 Conclusions: Chapter 1
From the contents of this chapter the overall project objective has become clear and
broken down into sizeable sections that can be completed individually. The content of
required research has been outlined and a set of performance guidelines has been
created to show the true desired outcome. These are all vital parts of the project if the
objectives are to be met successfully.
The following chapters will detail each of the sections outlined in chapter one and
explain in full the requirements, complications and decisions relating to each aspect.
The majority of this dissertation will detail the design, construction and testing of the
Mobile Manoeuvring Robot.
4
CHAPTER 2
LITERATURE REVIEW
The purpose of this literature review is to discover and critically analyse similar
concepts to that of the Mobile Manoeuvrable Robot.
This will build a suitable
framework to commence work and research on the project.
The literature view will comprise of the following aspects:
1. Brief Background on the concept of autonomous control
2. Is there a need for autonomous appliances/applications
3. What is the most suitable method of sensing distances?
4. What methods are best used for object avoidance?
5. Research of previous implementation of dual motor drive systems.
6. Discussions and Implications of autonomous technologies.
2.1 Introduction
The use of automated or autonomous robotic control is not a new concept. Many
people have dedicated their careers into designing these machines for many different
areas and many different applications. The military uses robots as war machines, such
as the TALON robot. The picture below shows a block of C4 explosive being placed in
the claw of the robot. Other military uses include safe bomb diffusion by use of robots
such as the following TELEROB. The robot can be safely sent into a dangerous
environment without the risk of losing human life. This means bombs can be diffused
faster and safer.
5
http://www.army-technology.com
Figure 2.1: Army Bomb Deployment
State-of-the-art remote bomb disposal
technology, the telerob Explosive Ordnance
Disposal and observation robot tEODor. The
German Army model is equipped with five
cameras and a double shot disruptor type
Richmond RE70.
http://www.army-technology.com
Figure 2.2: Bomb Disposal Robot
A more closely related topic is the automatic vacuum cleaner. These units commonly
use ultrasonic sensors to navigate around the room cleaning as it goes. Boundaries can
be set using magnets and the unit is sensitive to drop-offs such as stair wells.
A
common example of this is Electrolux’s Trilobite which is now commercially available
at retail stores.
6
2.2 The Need for Autonomous Applications
Imagine never having to wash, iron, clean or cook again. A robot could do it all for you
while you sit back and relax. To some this seems like the perfect world, while to others
it seems unethical and truly against their beliefs.
The demand for autonomous
applications is becoming ever more increasing and public acceptance is also on the
increase.
The company ‘Poly Micro’ argued in their 2004 newsletter that autonomous appliances
will grow because of consumers increasing expectations of energy and water saving,
noise reduction and overall efficiency and functionality. They also bring to focus that
more technology is being accepted within society. The following graph from poly
micros 2003 newsletter shows the acceptance of new technology relating to the
automation of driving systems within a manned vehicle.
Poly Micro predicts that by 2010 autonomous driving will be largely accepted as
practical by society. New cars of today are considered dangerous not to have an airbag
whereas 20 years ago this technology was not heard of.
Although this data varies slightly from this dissertation work, the trend of need and
acceptance through time is accurately portrayed in Figure 2.3.
http://www.polymicro-cc.com/site/pdf/POLYMICRO-markets.pdf
Figure 2.3: Increasing technologies
7
The article “Appliances of the future’ states also that the need and expectations of this
type of technology are growing at an alarming rate. It also mentions that for ideal
autonomous work in the future that robots will need emotion such as fear, pride and
caution. How can a robot complete great work if it has no pride in what it does, and
how can it make decisions without a conscience?
Henrik Christensen suggests that autonomous robotics in the home is a great idea
however has not come far enough to really break into the household market. The cost is
simply too high in ratio to its functionality.
Overall it is evident that the need and acceptance for autonomous robots in the home is
ever growing. While some circumstances of future developments may seem unethical
the basic cleaning and entertainment robots are proving to be an accepted and sought
after item in the home.
2.3 Sensing Distances in Applications
There are many different methods available for the purpose of sensing distances. These
include sensors such as proximity, ultrasonic, infrared, magnetic and various others.
Which of these is most suitable for a household application?
The Electrolux Trilobite (vacuum cleaner) uses ultrasonic sensors to navigate around
the room. Most sensors work by emitting some form of light or frequency and waiting
for that emitted source to ‘bounce back’. Ultrasonic sensors use sound or frequency
whereas infrared uses an invisible light source to judge distance or proximity. Infrared
light is often also used in data transmission such as remote control for a common
television.
The robo-rats website (2001) shows several different methods of sensing distances and
details the connections and problems associated with the setups. It shows methods of
beam breaking, using infrared emitters and detectors; distance sensors, also using
infrared emitters and detectors; and photocell sensing.
8
From all of these details it seems that a very successful method of judging proximity,
and also possibly recognising distance, is to use an infrared LED (Light Emitting
Diode) and an infrared detector. When the robot is facing a wall or object within a
certain distance (unknown at this stage and variable) infrared light will reflect from that
object and be collected in the detector. The higher the voltage or current returned from
the receiver, the closer the object must be. To overcome the possibility of natural light,
containing infrared, affecting the functionality of this sensor configuration, it will be
necessary to clock the infrared emitter at a rate of 36 – 40 kHz. The receiver will also
have to be tuned in order to only recognise this frequency of light.
2.4 Object Avoidance
Many applications are beginning to incorporate object avoidance technology into their
design. Cars are becoming more autonomous, traction control for example, and this
technology is bound to move towards object avoidance. Reversing sensors can alert the
driver when an object is close to the rear of the vehicle. It is only a matter of time
before a car will be able to recognise which lane it is and manage the steering system to
ensure it does not cross any lines. This technology is sure to save many lives from the
hazard of driver fatigue.
Object avoidance technology is currently installed into many items such as automatic
vacuum cleaners, auto lawn mowers and other items where little human instruction is
desired. Electrolux’s Trilobite automatic vacuum cleaner uses random driving while
avoiding collision in order to cover the floor space.
A project conducted by a student at Niagara Technology University used sensors and
hardware to create a object avoiding robot not dissimilar to that of this dissertation. The
concept behind this project gave the robot a human like thought process in that it would
come to an object, view the left then view right and make a decision of which way was
best to turn. If the robot had cornered itself then it would turn around and continue
driving.
David Tunnel 2004 suggested that there was no perfect solution available for
autonomous object avoiding and hence started a proposal to create an algorithm to
9
perform this operation. The proposed algorithm is intended to create a logical path for a
unmanned vehicle to take by use of sensors, videos and imaging data. ‘Our focus is to
develop a object avoidance algorithm called SmartAvoidT that extracts multiple
objects/targets out of video/imagery data, establishes individual tracks for each object
and maps a path around each object to avoid collisions.’ (Tunnel D 2004).
This
algorithm would then be implemented into the vehicles navigation system in order to
follow the calculated path. The algorithm will be designed to work in all weather
conditions such as day, night, rain, smoke or any other condition.
Koren Ward suggests that a successful method of controlling object avoidance is for the
robot to ‘learn’ methods and trends associated with traversing different situations. This
concept still utilises sensors and logic however has another much more complex
learning ability. The unit will record its previous experience with regard to the readings
from its sensors and so will be able to make a decision based on what occurred last
time. For example if sensor 1 was blocked and sensor 2 was clear then it will perform
in the same way as it did last time as long as last time encountered no errors. If errors
occurred it will try a different method and compare the results. This is a very complex
concept however it would most likely produce the least amount of errors in the long run.
A basic logic system may encounter the same error repeatedly, whereas this use of a
fuzzy logic learning system should prevent this occurrence.
While there are several methods of controlling a robot to avoid objects many are much
too complicated for the general purpose of this dissertation. This dissertation aims to
create a base model of an autonomous robot and so the programming of object
avoidance will be kept to a simple level. The concept described by the technology
student above is the initial concept decided upon for this dissertation. Giving the robot
a set of hard coded rules once it reaches an object should give satisfactory performance
while maintaining a simpler approach.
The coded instructions might look something close to the following:
START
Drive in a straight line until interrupt from sensor occurs
Is left sensor clear?
10
If yes turn left
If no, is right sensor clear?
If yes turn right
If no then reverse out or turn 180 degrees
Continue in a straight line (loop to START)
2.5 Dual Motor Drive Systems
Many systems use dual motors for directional control. A dual motor drive system refers
to having one motor for each drive wheel also known as ‘differential drive’. Both
motors driving forwards will make the unit move forwards; one motor forwards and one
motor in reverse will result in the unit turning etc. A well known example of this drive
system is in a skid steer (commonly known as a Bobcat). This method gives excellent
directional control and ‘on the spot’ turning allowing for tight corners and superior
manoeuvrability. The major problem with this method however is that one motor will
always turn slightly faster than the other resulting in the unit driving in a slight curve.
This may be due to efficiencies in the motors, gearbox friction, wheel to ground friction
and other uncontrollable factors. Some form of odometry for each wheel will be
necessary to ensure that the unit manoeuvres in a straight line.
This issue of non-straight driving is very common among robot builders and has been
overcome in several different ways. Many choose to change the drive system to a more
car like drive system with a single drive motor and steering mechanism. This is not
practical in many cases as it will sacrifice functionality.
The problem has been
overcome before by pulse-width modulating the two drive motors and counting the
edges on the encoders located at each wheel. This seems to be a very successful method.
Knudsen J 2000 refers to a similar method of counting the revolutions of the drive
shafts and comparing the number or revs on each side. All of this information is based
on LEGO™ components however the methods are still relevant. It also explores the use
of a mechanical differential to ensure straight line driving is obtained. This is very
similar to a car differential however is used in a different manner. By attaching the two
drive motors to where wheels would normally be connected, the differential will not
11
rotate unless the motors turn at different speeds. By monitoring the differential with a
sensor algorithms can be written to control the navigation.
For the purposes of this dissertation the clearest method is to use sensors on each wheel,
or better yet on the actual drive motor, to measure the revolutions and therefore distance
travelled. An algorithm will be written to ensure both drive wheels rotate at the same
speed.
This method will become very useful if time permits to increase the robots performance.
If this goes ahead the robot will use a method known as ‘dead reckoning’ where it
calculates its position as a sum of how far and in what direction it has travelled since its
origin. Although this is a rather inaccurate approach it is far simpler than any Global
Positioning Systems (GPS), especially in such a small application.
2.6 Consequential Effects and Outcomes
The final outcome of this project provides a base model for intelligent household
applications such as cleaning, object retrieval or similar. The extent of this project will
not extend to a final product suitable for marketing but is just the base concept.
The research and technical outcomes from this project pose no direct ethical or legal
dilemmas however if this concept is extended on then some factors may need to be
considered.
Many engineers and scientists are still studying the use of autonomous vehicles for
many different purposes in many different fields of expertise. From military through to
agriculture robots are becoming more frequently relied on and the need for more
advanced technology is ever increasing.
Military and federal applications of robots include the use of technology to diffuse
bombs or clear areas where the risk of losing human life is too high. Similar to this is
the use of robots to track through rubble from collapsed buildings or landslides to
search for survivors and perform simple medical checks. NASA uses autonomous
robotics for missions such as Mars Rover discovery and other distant missions.
12
Although most of these cases still rely on human instruction, usually from remote
control, they are all still based on a similar content to the technical side of this
dissertation.
Future development of this idea of autonomous mobile navigation may result in any
number of new designs. Some of these may be:
•
Concept cars able to drive without human instruction. May be used for
taxi services or courier and mail delivery.
•
A similar service to ‘Guide dogs for the blind’, helping blind members of
the community to be self sufficient.
•
Automatic cleaning of bathrooms, kitchens and offices. Reducing the
need for maids and cleaners.
Some of these future developments pose some ethical questions however. Is it right to
make a machine that will put people out of work? What if the automated robot causes
damage to humans or property and is not able to be controlled? What if an automated
car crashes, killing a family with young children? Who takes the blame for any of these
circumstances? It is a very controversial subject with many sides to each argument.
Many movies have been created which discuss the possibility of robotics in the future.
Humans create machine with such intelligence that they become uncontrollable. ‘The
Matrix, 1999’; ‘I Robot, 2004’ and ‘Stealth, 2005’ all discuss the implications of errors
in machines that have turned into drastic situations. Although these are most likely far
fetched extremes, the concept is a possibility. Electronic components, such as solenoids
and sensors, can easily fail which might make a car miss a turn or fail to brake. It once
again poses questions if it is right to put a human’s life in the hands of a machine.
13
2.7 Summary: Chapter 2
To summarise the literature behind the concept of a mobile manoeuvring robot it is
obvious that most of this technology has been invented before. The content that will be
covered in this dissertation will be on the basis of autonomous technology and hence
will most likely not be an extension into new technology or concepts. The basis for this
project is to explore and understand the basic essentials in an autonomous situation that
may be used for any industrial or commercial purpose.
14
CHAPTER 3
RESEARCH DESIGN AND METHODOLOGY
Before commencing any of the construction or completed design of any of the
electronic or mechanical components, it was necessary to undertake some certain
analysis. A safety analysis and a resource requirements and acquisition table was
completed to fully understand the background, direction and precautions to consider
whilst the project was under design and analysis.
3.1 Safety Issues
Safety is a relatively low concern in this project. While various factors require some
attention, there are no large definite risks such as chemical handling. Saying this
however does not mean that there is no cause for concern along the duration of this
project. The following risk assessment outlines the primary hazards and methods of
reducing the risk.
Constructing anything mechanical brings with it some risks. The construction of this
mechanical unit involves cutting, grinding, drilling and using other power tools on
products such as aluminium and timber. Bushes are also to be made from industrial
grade plastics on a lathe. On the electrical side of this project a lot of soldering and
drilling/screwing will also take place.
The possible hazards and risks of these
operations are listed below.
3.1.1 Mechanical Safety Issues
Cutting aluminium with drop-saw or similar
Occurrence
likelihood
Consequence
H/M/L
Controls to
avoid injury
Risk after
controls
Loud Noise
High- Aluminium
is a noisy material
to work with
H – Hearing
Damage will occur
for multiple cuts
Hearing protection
must be worn
L – Small amount
of cuts no problem.
Flying debris
High – Hot spatter
from saw blade
will fly
H – Blinding if
caught in eyes,
minor burns
possible on skin
Eye protection to
be worn, Face
mask preferable,
non-loose – long
sleeved clothes
L – Adequately
protected
Saw jamb
Medium – If work
not secured piece
may fly
H- possible loss of
fingers in blade or
pinching of skin
Clamp work piece
when cutting
L – If clamped no
problem
Hazard
Table 3.1: Cutting aluminium safety
15
When grinding, ensure that the appropriate sized grinder is used. For example, a nine
inch angle grinder used on a small piece of aluminium is likely to cause damage to
either operator and/or work piece.
Grinding/ Die grinding
Occurrence
likelihood
Consequence
H/M/L
Controls to
avoid injury
Risk after
controls
High- Grinding is a
noisy operation
H – Hearing
Damage will occur
for long use
Hearing protection
must be worn
L – Small amount
of cuts no problem.
Flying debris
High – Hot sparks
from blade
H – Blinding if
caught in eyes,
minor burns
possible on skin
Grinder jamb
Medium – If work
not secured piece
may fly
H- possible loss of
fingers in blade or
pinching of skin
Hazard
Loud Noise
Eye protection to
be worn, Face
mask preferable,
non-loose – long
sleeved clothes
Clamp work piece
when cutting, use
appropriate grinder
L – Adequately
protected
L – If clamped no
problem
Table 3.2: Grinding and die grinding safety
When using any power tool ensure correct tools and attachments are used and
appropriate user knowledge of the operation is known.
Drilling and other power tools
Occurrence
likelihood
Consequence
H/M/L
Controls to
avoid injury
Risk after
controls
Loud Noise
Med – most power
tools create some
loud noise
M - Hearing
Damage will occur
for multiple cuts
Hearing protection
must be worn
L – Small amount
of cuts no problem.
Flying debris
High – Hot spatter
from saw blade
will fly
H – Blinding if
caught in eyes,
minor burns
possible on skin
Eye protection to
be worn, Face
mask preferable,
non-loose - long
sleeved clothes
L – Adequately
protected
Tool jamb
Medium – If work
not secured piece
may fly or spin
H- possible loss of
fingers in blade or
pinching of skin
Clamp work piece
during work
L – If clamped
problem minimised
Hazard
Table 3.3: Drilling safety
Lathe work
Hazard
Occurrence
likelihood
Consequence
H/M/L
Flying debris
High – Hot spatter
from saw blade
will fly
H – Blinding if
caught in eyes,
minor burns
possible on skin
High speed
operation
M- Chuck and
work piece
spinning
H- loss of fingers
of large cuts and
abrasions
Work piece fly
M- chuck slip or
error in clamping
H- building damage
or personal injury
Saw jamb
Medium – If work
not secured piece
may fly
H- possible loss of
fingers in blade or
pinching of skin
Controls to
avoid injury
Eye protection to
be worn, Face
mask preferable,
non-loose - long
sleeved clothes
Experienced user
present, caution
used when
operating
Ensure piece
clamped, be aware
of possible piece
release
Clamp work piece
when cutting
Table 3.4: Lathe safety
16
Risk after
controls
L – Adequately
protected
M- Impossible to
remove spinning
component
M- Impossible to
reduce risk to a
low level.
L – If clamped no
problem
Painting
Occurrence
likelihood
Hazard
Med – many
fumes present
Toxic Fumes
Consequence
H/M/L
Controls to
avoid injury
M – Eye and
respiratory damage
Eye protection to
be worn, fan or
dust extraction
present, ventilated
area
Risk after
controls
L – Adequately
protected
Table 3.5: Painting Safety
3.1.2
During The Electrical System Creation:
Soldering
Occurrence
likelihood
Hazard
Consequence
H/M/L
Toxic Fumes
Med – many
fumes present
raising upwards
M – Eye and
respiratory damage
Hot solder
dripping
Low
M- Mild burns to
skin
Hot iron
Med. Touching
will leave instant
burns
M – Possible mild
burns
Controls to
avoid injury
Eye protection to
be worn, fan or
dust extraction
present, ventilated
area
Clear work area in
standing position.
Adequate clothing
Clear work area
and use caution
Risk after
controls
L – Adequately
protected
L- Caution will
mean no burns
M – unavoidable
other than caution
used
Table 3.6: soldering safety
3.1.3
During The Testing Procedure:
Although testing seems very straight forward, there are still several hazards to
be aware of. User hazards are minimal however damage to hardware and
property is still possible.
Testing
Hazard
Occurrence
likelihood
Consequence
H/M/L
Controls to
avoid injury
Risk after
controls
Object avoiding
fails
Overload or short
circuit
microcontroller
M- sensor fail,
code error
M – surge in power
or error in
connection
L – small scratches
on objects
L- no damage will
be caused
Power sources
Med – voltage
shocks
Use test blocks
which can be hit
Careful
connections, use
overload protection
Understand power
pack before use.
Tape or hide high
voltage wires
H – Expensive
microcontrollers
H – if large voltage
touched,
electrocution
possible
L- microcontroller
protected
L- High voltages
avoided.
Table 3.7: Testing safety
3.2 Resource Requirements
There are many components to this project which will be sourced from a widely varied
field. Due to the nature of this project it will be constructed on a tight budget. This
means aesthetics and practicality may suffer to some degree. Most resources will either
be scavenged from existing products or borrowed from institutions such as USQ where
possible.
17
The required resources can be categorized into two major fields, mechanical and
electronic. The following explains these categories and the planned source.
Mechanical components/resources:
Resource
Description
Requirements
Source
Back-up Plan
Unit chassis
Aluminium 100x100
box section
Light weight
Scrap bin at Patio shop
N/A
Motors (x 2)
12V Low Amperage
Purchase (Bunnings
XU1 cordless drills)
N/A
Gear box (x 2)
Windscreen wiper
motor (XD Falcon)
Minimal weight, large
reduction
Car wreckers
N/A
Trundle wheel
Low friction small
trundle wheel
Light weight
Old cupboard wheel
N/A
Fastenings (rivets,
screws etc.)
Assorted
N/A
Family Workshop
Hardware Purchase
Wheels
115mm diameter
Light weight
Pram wheels
Hardware Purchase
Bushes etc
Assorted
Low friction, light
weight, affordable
Create in workshop
Second hand toys
Table 3.8: Mechanical resources
Electronic components
Although there will be many components required that are unknown at this stage, the
following table provides a basic plan for the sourcing of components.
Resource
Description
Requirements
Source
Back-up Plan
Microcontroller
Motorola HC12
---
USQ on loan
Purchase chip and get
soldered to PCB
Infrared LED + sensors
Various
---
Electronic shop
Internet purchase
555 timers
---
---
Electronic shop
USQ loan
Wiring
Various colours
---
Electronic shop
USQ
Table 3.9 Electronic Resources
3.3 Sustainability
Unfortunately it will not be practical to keep the robot assembled at the completion of
this project. Due to the major component (HC12 microcontroller) being unaffordable to
the budget, the robot will be useless after the return of components. Without the
microcontroller the rest is rendered futile.
18
At the conclusion of this project several components will be returned.
The
microcontroller will remain the property of USQ. The windscreen wiper motors will be
beyond repair but may be reused in other applications. Wheels and other mechanical
components will be returned to the workshop. The electronic components will be kept
for other applications where sensors etc can be used.
3.4 Methodology
The following project goals were created in chapter one and are re-listed in
methodology so as to set the basis for the structure of this dissertation. The project
work outlined in this dissertation is based entirely around this methodology.
By pursuing the following goals the project objective should be reached satisfactorily
and efficiently.
1. Define a guideline to assess the performance of the robot to the specifications of
the project objective.
2. Build a prototype that is practical to the objective
3. Research the background behind obstacle avoidance and other attempts to
achieve similar tasks.
4. Research microcontrollers and sensors to acquire the most practical
configuration as to meet the objective.
5. Define an initial design of the configuration and code to be implemented.
6. Construct initial design
7. Test and analyse the results in accordance to the performance guidelines.
8. Re evaluate the design as required to achieve the project objective.
As time permits
o
Define a new performance guideline for the practical task completion
o
Research more methodology if required
o
Re design and construct the robot to achieve the new objective.
o
Test and analyse the results in accordance to the new performance guidelines
o
Evaluate and change the design as required to achieve new objectives.
19
3.5 Justification of Methodology
The methodology above has been chosen carefully to complete the project objectives.
The first step of ‘Define a guideline to assess the performance of the robot to the
specifications of the project objective’ has been chosen to give the robot a set of
guidelines to be assessed against. Without having this goal, it will be impossible to
determine if the robot has met all requirements. Goal three, Research the background
behind obstacle avoidance and other attempts to achieve similar tasks, will give
background knowledge behind the concept. This can save a lot of time in decision
making processes as it may help predict the outcomes based on previous experiences.
The design stage is the next logical step and is carried out as goal four. The testing
stage is very important and is closely linked with goal one of the performance guideline.
The robot must be tested and assessed against these guidelines in order to understand
which parts of the robot were successful and which aspects need more work.
The methodology of the time permitting guidelines can be justified in the same manner.
It is a very similar process with most of the background information already known.
20
CHAPTER 4
Construction and Design
4.1 Initial Design
Several ideas were analysed before the initial prototype was built. The mechanical
structure of the robot was a major consideration. Wheels versus tracks, mechanical
steering versus dual motor drive and other considerations along with shape and
dimensions were the chief factors.
Initial analysis of these ideas provided a dual motor, two track setup with a wide wheel base for stability. This design is shown in figure 4.1 below.
Figure 4.1: Initial Chassis Prototype
This design seemed very practical for this application due to its small centralised
arrangement, its excellent turning circle and ability to manoeuvre.
The problem
occurred however when the drive motor could not gain sufficient traction to the rubber
track. Several different ‘drive hubs’ were implemented to attempt to overcome this
problem however the rubber tracks were too flexible with a very small coefficient of
friction.
The setup required to make this arrangement successfully work far out-
weighed the practicality of the design.
21
The motor slipping in the tracks would have made this project a near impossibility
without a delicate error correction system in place. Because of these difficulties a
decision was made to use wheels connected as a direct drive to the motor.
4.2 Second Prototype
The second prototype for the mechanical design consisted of an aluminium chassis with
dual drive motors. A simple trundle wheel for stability was used to allow ‘on the spot’
steering and high manoeuvrability.
Figure 4.2 Second Chassis Prototype
The drive motors were chosen from a set of affordable ‘XU1” 12 volt cordless drills.
The speed of these motors was far too fast to attach directly to the drive wheels of the
robot however, so a gearbox was required.
A worm drive seemed the logical
arrangement for this to provide high reduction, high torque and very minimal backlash.
Two windscreen wiper motors from XD Falcons were purchased from a car yard and
modified to suit the desired purpose. Due to the size of this application, batteries will
be small and therefore the motors need to be of low power consumption. Windscreen
wiper motors draw approximately 5-10 amps and so running two of these would require
a rather large battery. By replacing the original motors with the cordless drill motors,
the amperage was dropped to approximately 5 amps for both motors running
simultaneously under load. Figure 4.3 shows the small motor mounted on the gearbox.
22
Figure 4.3: Motor setup
Figure 4.4: Chassis design
The chassis is a 100 x 100mm box section of aluminium commonly found on patio
posts. The axle holes were formed with a die grinder and are designed for the motors to
bolt straight into. The trundle wheel was placed on temporarily until final dimensions
are known for extra hardware (batteries, microcontrollers, wiring etc).
4.3 Odometer Sensors and Interrupt Control
4.3.1 Building the odometer sensors
As explained earlier, it is necessary for the Mobile Robot to be able to drive in straight
lines between obstacles. For this to occur it is necessary to calculate the turns of each
wheel (or motor) to compare against the other. There are various methods available for
this; however the easiest and most successful technique is to insert a sensor on each
motor to count the revolutions. In this case an infrared LED and receiver have been
used to count the revolutions. Figure 4.5 shows how this sensor is implemented.
Figure 4.5: Odometer Sensor
23
The LED (DSE part number Z3235) and Infrared Receiving Diode (DSE part number
Z1956) are mounted in an outer casing that mounts the motor to the gearbox. A 4mm
hole is drilled through the motor drive shaft which aligns the LED with the Receiving
Diode twice for every revolution of the motor. From this circuitry it is possible to obtain
a 5 volt drop for every time the sensor is aligned.
Figure 4.6 Single Hole odometer sensor
To obtain the 5 volt drop it was necessary to fiddle with resistor values on the 5 volt
input rail to the receiver. The resistor value was dependent on how much of the hole
aligned, the intensity of the infrared beam coming through the hole and also the
brightness of the outside light. (Incandescent light bulbs and sunlight contain masses of
Infrared.) To overcome the variance of the outside light, a film of white gap filler was
applied over the receiver to completely isolate all of the surfaces from any source of IR
other than the emitter. A guess and check of values found that when a 68 kilo ohms
resistor was placed in series in the power supply for the receiving diode, a five volt drop
(5v to 0v) was obtained when the sensor aligned. See circuit below for details.
Figure 4.7: Odometer Sensor Circuitry
This circuit can be used to generate an interrupt for use in the microcontroller. It is used
on the high to low edge however can be used in either edge sensitive case.
24
4.3.2 Using interrupts to count odometer readings
The circuitry detailed earlier was designed to provide a 5v drop twice for every
revolution of the motors shaft. This 5 to 0 volt drop provides the perfect setup to use in
one of the many Motorola HC12 interrupts.
The Motorola has many different interrupts with varying priorities and ideal uses.
Some forethought was applied to the needs of interrupts and it was considered that the
odometry sensors would need the highest priority.
This would allow other lower
priority interrupts to run without effecting the counting of motor revolutions. A first
attempt was to use IRQ and XIRQ to count each motor.
The first issue to deal with using this decision was that XIRQ is a level sensitive
interrupt. This meant that if the motor was rotating slower than the interrupt could
service (and obviously this would happen with an 8Mhz processor and the robot only
moving at about 0.2m/s), then the interrupt would run repeatedly whilst the IR LED and
the Receiving Diode where in line. To overcome this, a flip flop was set up to trigger
on the falling edge of the signal and then it would be reset by a wire coming from Port
A.
The concept behind this seemed logical and straight forward however many
problems arose for various reasons. Figure 4.8 shows the Flip Flop configuration
implemented.
Figure 4.8: 4013 Flip-Flop configuration
25
The above arrangement of a 4013 Dual D Type Flip Flop is set to work on a rising edge
(0 to 5 volts). Using a falling or rising edge will not affect the accuracy of the counting;
it will still see two rising edges every rotation of the motor. When the sensor rises from
0v to 5v, the flip flop is triggered and Q NOT changes from high to low which triggers
the XIRQ (active low) interrupt. Before the end of the interrupt service routine, a logic
high can be sent from PORT A to reset the flip flop and await the next rising edge from
the sensor.
This concept did not work when attached to the sensor and microcontroller. When
voltages where manually applied to the flip flop slowly it would perform successfully
however when the process was applied through the XIRQ interrupt service routine, the
logic levels would not change appropriately. The IRQ interrupt was also not working
correctly. It was initialised to recognise falling edges but would not activate on the
falling edge coming from the sensors. It would however activate if an earth wire was
touched to it. It was decided that perhaps noise or other less obvious factors were
causing this.
There seemed to be too many problems for the simplicity of this idea so it was deemed
appropriate to disregard the use of XIRQ and IRQ for this purpose. The sensor wires
were connected to the PORT G key wake up port and instantly an accurate counter was
achieved. The major issue with this arrangement was to remember not to use any
higher priority interrupts to run a routine which would turn the motors in either
direction. This would make the position of the robot an unknown factor.
As a result of this testing the odometer sensors were made successful by simply using
an Infrared LED (DSE part number Z3235) and an Infrared Receiving Diode (DSE part
number Z1956) connected to the key wake up of PORT G and the software initialised
correctly to deal with this. A simple interrupt service routine was written to add one (1)
to the counter that recorded the revolutions of the respective motor. These counter
values are then available for calculating straight line driving or even position
monitoring.
26
4.4 H-Bridge Motor Control
After having the mechanical unit constructed, encompassing the microcontroller and
odometry sensors, it was necessary to decide on a method to control the motors. Two H
bridges were sourced from the technician’s lab at USQ to allow the microcontroller to
handle the large current flows. An H bridge works by a series of four switches which
can control the current flow through the motor. The schematic below shows the basic
operation of the common H Bridge. The grey arrows represent the current flow through
the motor.
Figure 4.9: Basic H Bridge Operation
By applying a small voltage such as logic high from the Motorola HC12, the switches
can be turned on to allow current flow and hence motor operation. Only diagonally
opposed switches should be turned on at the one time. If both switches on one side are
turned on at the same time a short circuit is made from the positive to negative voltage
supply. This is often referred to as shoot through.
27
Anything that can control a current is suitable for use as the switches in an H bridge
such as relays, transistors or MOSFETS. In this case, four MOSFETS have been used
with small heat sinks to cater for the 12V motors which are drawing approximately 2.5
amps each at full load.
One excellent advantage of using an H Bridge is that it reduces the voltage and current
spikes that occur from the motors starting, stopping or changing direction quickly. With
the Mobile Manoeuvring Robot the voltage spikes were still higher than the H Bridge
could contain. The cheap motors that were purchased for the drive have very poor
characteristics and were resetting the microcontroller every time that the two motors
turned on simultaneously.
There are several procedures that could have been
undertaken to overcome this problem. A more efficient pair of motors may have
produced less voltage spike; a large capacitor could have been implemented to provide a
spike filter; or the chosen method, to use separate power supplies to run the
microcontroller and the motors respectively. A 9 or 10 volt battery is ideal for running
the microcontroller as the voltage passes through a LM7805 voltage regulator. This
method has the added advantage of being able to have a separate, higher voltage battery
to run the motors without having to reduce it significantly to power the microcontroller.
Both power supplies must share a common earth for the robot to function correctly.
To control the motor speed requires more than just a logic high input to the H Bridge.
Motors will always run at slightly different speeds due to the internal friction losses and
other variances in efficiency and so the robot would drive in large circles. Pulse Width
Modulation (PWM) is a very successful method of controlling the speed. By applying a
chosen frequency to both motors and then adjusting the duty cycle, the motors speed
can be controlled.
The Motorola HC12 has 4 channels dedicated to pulse width
modulation. Bits 0-3 of PORT P can easily be set to output a controllable pulse. This
provides a perfect environment to control two motors, one channel for each motor in
each direction.
The four PWM pins (PORT P pins 0-3) are connected directly to the H bridge inputs.
Simple software initialisation sets the ports ready for PWM and sets a frequency to base
the duty cycle around. For the Mobile Manoeuvring Robot a pre-scaler divider of 128
is used to divide the 8MHz processor down to create a slower clock that can be used to
28
control the frequency. By setting a number between $01 and $FF in the PWPER (0-3)
registers, the pulse frequency can be set to a proportion of this clock rate. The duty
cycle of this frequency can then simply be controlled by storing values between $00 and
$FF into the PWDTY (0-3) registers. This value represents the proportion of high over
low time; hence $FF/2 would be 50% duty cycle and the motor would be running at half
speed, or $00 would stop the motor.
It is important to not switch the H Bridge switches too fast in this application.
Transistors require a small amount of time to switch on or off. It is because of this time
that causes a current flow and hence a power loss. Over switching at high frequencies
will increase the power consumption and therefore create heat from the MOSFET’s.
Heat sinks are installed on all of the robots MOSFET’s to compensate for the switching
power loss.
To conclude on motor control, the Mobile Manoeuvring Robot is controlled by two
identical H Bridges which are powered from a 10 – 12 volt source. The motor speed is
determined by four separate Pulse Width Modulation Channels with a relatively low but
fixed frequency and variable duty cycle.
4.5 Infrared Distance Sensors
4.5.1 Requirements and Availability
The current market offers many types of sensors for use in various applications. A few
of the major types of sensors include:
•
Optical sensors
•
Photo diode sensors
•
Fibre optics sensors
•
Proximity sensors
•
Ultrasonic sensors.
29
For accurate manoeuvrability in this application it is necessary that the sensors have a
long enough range to avoid collision during turning. Figure 4.10 illustrates this need.
Figure 4.10 Sensor Distance Requirements
The above diagram illustrates that even after the robot has stopped to avoid an object,
the turning circle will result in the corner of the robot still proceeding forwards. It is
necessary for the sensor to be able to read further than this turning circle. The necessary
distance can be reduced significantly by turning the outside wheel backwards so it pulls
away from the wall, this however does pose the issue of being able to reverse into
objects, as there is no rear sensors.
Also, when in this illustrated position, it would be preferable if the sensors could judge
a long distance at the sides of the robot. If the robot where to turn left after stopping in
figure 4.10, it would turn directly into a wall and be interrupted by the side sensor half
way through a turn. This would make coding of the processor more difficult. Initial
experimentation has shown the ideal range of the sensors will be approximately
200mm-300mm but definitely no less than 100mm for the front sensor.
Furthermore, for household applications the obstacle to avoid may be the wall. If a
short range sensor is used and placed above the skirting board the wheels may impact
this before the sensor realises there is an obstacle. This will result in scratches on the
obstacles and possible breakage of the robot. Also, the robot will be jammed until loss
of power or failure of components.
30
4.5.2 Choice of Sensor
Almost all of the current household applications that require distance or proximity
sensing utilise Ultrasonic or Infrared Light (IR) sensors. The market available choices
are large and vary in specifications and range in price from around $40 - $120 each.
Many hobbyist robot builders choose to construct IR sensors to save a lot of cost and
custom design them to suit the necessary requirements.
For the purpose of the Mobile Manoeuvring Robot, it was decided to construct three
separate Infrared Sensors from parts commonly available at electronic stores.
4.5.3 Design and Construction of IR Sensor
The design and construction of the Infrared sensors took a very large portion of the time
and effort spent on this project. Lack of information on the chosen parts made it
difficult to realise their true operations and many other factors postponed the successful
creation of the sensors.
After thoroughly researching other robot builders’ attempts to build IR sensors, a
commonly available 38 KHz receiver was chosen from Jaycar Electronics along with
the same IR LED’s used in the odometry sensors. To tune the IR light suitable for the
receiver it was decided to use a 555 timer in astable operation to pulse the light at a
square wave at 38 KHz with a duty cycle of 50% in accordance with the data sheet of
the receiver. This circuit was simple to construct and the schematic shows the detail
below in figure 4.11.
31
Figure 4.11: 555 Timer Pulsing Sensor Light
Initial calculated results differed substantially from the measured performance. It was
necessary to connect a Cathode Ray Oscilloscope (CRO) to accurately measure the
waveform output. Slight tuning of resistor values provided an accurate 38 KHz square
wave with 50% Duty Cycle.
The transistor is required on the output of the 555 timer to source the current needed to
supply the three IR LED’s. Each LED can handle 50mA constantly running through
them, however due to the 50% duty cycle; the LED will only be on 50% of the time. It
can then be safely assumed that the LED’s can actually handle 100mA as long as they
are only run through the 555 timers pulse.
To contain the IR LED and project the light in the desired direction, it was decided to
modify and use some discarded LED keychain torches. After removing the batteries,
switch, resistor and white light LED; an IR LED along with the 50 ohm resistor were
soldered on to the Printed Circuit Board (PCB). From the PCB, two wires were run out
the back of the torch to the 555 timer circuit and then the unit sealed to prevent any IR
light escaping which would create undesirable results. Figure 4.12 and 4.13 show the
torch modified into an infrared emitter.
32
Figure 4.12: PCB Inside LED Torch
Figure 4.13: LED Torch Complete
With Wires
The IR receiving diode should have responded with a voltage drop or even a noticeable
resistance change when presented with the torch; however no change was found
whatsoever. To check the frequency response of the chip, a function generator was
hooked into the base of the transistor at the output of the 555 circuit. The chip was
tested for response from 1 Hz up to a few hundred kHz but absolutely no response was
found. No datasheet was available for this chip as it was sold solely and had no
markings to distinguish it by. After reading other circuits that seemed to contain similar
chips, it was found that a pull-up resistor was most likely necessary for correct
operation. By adding a 2k2 ohm pull-up resistor to the output of the receiving chip a
change of approximately 0.5V could be obtained over a distance of 100mm. This was
far from ideal however a comparator circuit would be able to turn this small analog
signal into a clear digital response. It wasn’t until the comparator circuit had been
constructed on a breadboard that it was found that sunlight shining through a window
was affecting the response of the sensor. Due to the large complexity of the comparator
circuitry to achieve such a simple task, it was decided to scratch this idea and start from
a different perspective.
After a lot of searching on the internet for different IR receiving components, a DSE
component, part number Z1955, was discovered that claimed to provide a digital signal
in relation to the presence of 38 kHz light. This seemed much more practical than the
analog signal chips, as measuring distance is not a requirement of the Mobile
Manoeuvring Robot. After powering up the new chip and shining the torch off the 555
timer circuit a 5V drop could be obtained over a distance of approximately 500mm.
33
This was ideal for the purpose of the robot and so more of these chips were obtained.
The Z1955 datasheet details a suggested bypassing and filtering circuit containing a few
resistors and capacitors. A single circuit board was soldered containing three of these
bypassing and filtering circuits and three receiving chips. Testing of these revealed that
the first prototype circuit still worked fine, however the two new circuits (identical in
every manner) would only work at a distance of approximately 20mm. Due to the fact
that one of the receiving circuits worked successfully, the mistake was made of
assuming that the IR transmitter circuit was without fault. It wasn’t until after many
hours of testing and different circuitry being implemented that it was found to that the
555 timer circuit was causing relatively large voltage spikes in the power supply in time
with the 38 kHz light pulse. Due to the fact that the emitter and receivers were being
powered from the same voltage supply, the noise was affecting the operation of the
receiver chips. It is still unsolved why one chip worked and the remaining two failed;
however overcoming this problem initiated some desired results.
A group of capacitors wired in parallel on the input of the transmitter circuit provided a
noise filter to the power supply. A combination of a large Electrolytic capacitor,
medium Tantalum capacitor and a small Monolithic capacitor provide an effective noise
filter to combat fast ripples in the power supply. The following schematic details the
chosen capacitors and placement in the power supply circuitry.
Figure 4.14: Power Supply Filter for Transmitter
An LM7805 voltage regulator is used to supply the 5 volt source from the same battery
that supplies the Motorola HC12.
34
The noise filter, illustrated in figure 4.14, reduced the noise to a negligible level. From
this, the Z1955 receiving chips delivered a different behaviour. First experiments on the
bread board provided three working receivers over a distance of approximately 300400mm shown by a 5V drop.
As this was suitable performance for the Mobile
Manoeuvring Robot, the circuitry was soldered to a circuit board. Testing at a later date
showed none of the circuits working again. After another long, strenuous testing period
it was discovered that the Z1955 chips were also sensitive to sunlight and incandescent
light, despite the claims of the data sheet. If an IR light source was provided to the
robot, such as an incandescent bulb, the sensors would work successfully to a distance
of approximately 300 mm. Without the additional IR light source the sensors would
sometimes work at a distance of 20 – 30 mm.
To overcome this problem it was finally decided to implement some variable brightness
IR LED’s to supply IR light to the back of the receiving chips. The Z3235 LED can
handle at most 50mA constant current. A 1k variable resistor was implemented in
series with a 100 ohm resistor so to provide a variable current which could not exceed
50 mA. Calculations prove that the current can be varied between 4.5 and 50mA:
I MAX =
V
RMIN
I MIN =
(5)V
(100 + 1000)Ω
= 4.55mA
(5)V
(100 + 0)Ω
= 50mA
=
=
Where:
V
RMAX
I = Current flowing through LED [Amps];
V = voltage drop across LED [Volts];
R = resistance in series with LED [Ohms].
At 4.5 mA the Z3235 LED is hardly on but does produce some IR light. This variable
brightness light provides a method of controlling the sensitivity of the IR receiver and
hence a control of the distance sensed. The IR LED’s provide enough IR to ensure
successful operation of the receiving chips and hence the accomplishment of the
distance sensors.
35
Figure 4.15 gives an overview of how the pulsing IR LED, Receiving diode and
variable IR LED are positioned to provide a successful distance sensor.
Figure 4.15: Position of Sensor Components
The Z1955 IR Receiver is mounted onto the torch containing the pulsating IR LED.
This provides an ideal position to pick up any objects located directly in front of the
sensor. A wider sensing range could be created by shortening the outer housing of the
torch or using extra pulsating LED’s concentrating in the desired direction.
The sensors are mounted to point in each possible direction of travel. This includes a
front, left and right sensor. The code is designed to stop the travel of the robot if
anything activates one of the sensors and then perform a task specific to the status of
each sensor. The figure below shows the mounting of the sensors.
36
Figure 4.16 Sensor mounting on the Robot
There were two main options to communicate between the sensors and the
microcontroller. Either the status wire from the receiver could be connected as an
interrupt to the microcontroller; or it could be connected as a data line to any available
port. Due to the fact that the robots guidance is more interested in knowing the current
status of each of the sensors rather than knowing exactly when each is triggered, using
the data line approach is far more effective. One advantage of this method is that noise
filtering can be used by checking the sensor a number of times to ensure there is
actually an object in front of the sensor and that the signal was not just caused by noise.
After checking the sensors, the robot can make an informed direction on which direction
to travel. Not using interrupts also allows checking of each of the sensors during any
part of the code or in any interrupt service routine.
Each of the sensors is connected to PORT A (pins 0-2). After originally connecting the
wires directly into the port so that when the sensor was active it would read logic zero
and non-activated would read logic one, it was deemed more practical if the data was
inverted. More accurate calculations can be made on this data and the code will be a lot
easier to understand and debug. To invert this data, a HD74lS00P (quad two-input
NAND gate) IC was used with the inputs of each individual NAND tied together to
37
provide inverters. The logic signal from the sensors was then applied through these
joined inputs and the output provided an inverted signal of the input.
The program code simply checks the status of each sensor in a loop by loading PORT A
into an accumulator and performing logic decisions on the value loaded.
The
microcontroller now reads a logic one for an activated signal and a logic zero for a nonactivated sensor. Hence, if all sensors are activated the register will read 00000111 or if
no sensors are activated it will read 00000000.
To summarise the distance sensors used on the Mobile Manoeuvring Robot the
following points can be observed.
•
Infrared LED’s (DSE part number Z3235) clocked at a 38 kHz square wave with
an even mark to space ratio are used for the transmission of the sensors light.
•
Buffered Infrared receiver chips (DSE part number Z1955) with the
recommended filtering and bypassing are used to pick up the transmitted light.
•
Extra IR LED’s with variable brightness are used to saturate the IR receivers to
ensure successful performance
•
The logic outputs of the sensors are inverted to communicate effectively with
the Motorola HC12
•
Sensor status is read in by the microcontroller as data on PORT A.
In retrospect to designing custom IR sensors for the simple use of obstacle detection, it
would be far more practical to spend the money on tuned sensors that work without
error. The robots sensors work reliably now; however an enormous amount of time was
spent on designing these which would have been more effectively used on the objective
and practicality side of the design.
38
4.6 The Software
The software used to control the Mobile Manoeuvring Robot was created in assembly
language for the Motorola HC12.
This allowed direct communication with the
microcontroller and convenient access to all of its ports and functions. The software
used to control the heading of the robot follows a relatively simple structure with small
subroutines for each separable function or routine. Interrupts are used for the odometer
counting and a tight loop in the main function keeps track of the direction of travel and
sensor readings.
A software design procedure (available in Appendix C) was used to analyse the problem
and deal with suitable specifications and provide an appropriate software structure. The
software design procedure encompassed the major points of software design; such as
objectives, user information and program structure. The objective of the software was
stated to be “To control the mechanical hardware of a two drive-wheel robot in order to
avoid collision with obstacles. The software must be able to control the unit to travel in
a straight line between objects and is based on assembly level language of the Motorola
68HC12 microcontroller.” It was necessary to base the software structure around this
as well as encompassing the user information. The user information is listed below.
User Information
The code has five sensors that input to the software. Three of these are obstacle
avoidance sensors read in as data through port A and the other two are concerned
with odometer readings read in as interrupts through port G. The program starts at
$0400 with data starting at $0200. The stack pointer must be set in a clear location
such as $0700 and the program counter to $0400 to start the procedure.
When run, the program will output through the serial port the status of the odometer
readings and also controls the speed and direction of both motors to achieve the
desired performance. The program loops continuously to give real time control the
mechanical components
From these listed objectives and user information, while also including any other
specific requirements, a structure was decided upon to control the Mobile Manoeuvring
39
Robot. It is in the form of a tight loop main routine that branches out when individual
activities require to be completed. The following outline was created to establish the
necessary activities to be completed in the main loop and the appropriate related
subroutines.
While driving do the following:
• Read the odometer sensors and increment odometer counters
o Check odometer counters and adjust speed for straight driving
• Watch obstacle sensors in a tight loop act accordingly when sensors
triggered.
o If left is clear, turn left otherwise turn right

If left and right blocked, reverse
• Continue on a straight path
• Output data through serial port for debugging purposes
• Repeat process continuously
The data will flow as follows, coming from the five IR sensors and being manipulated
and processed to obtain the required drive on the motors. There are four main processes
that take part in this data processing.
sensors
PORT
A
Obstacle
Process 1
D1
Process 2
D3
D5
sensors
PORT
G
D4
Odometer
readings
Process 3
D2
MOTOR
CONTROL
Process 4
D1 = Signal of which direction to turn
D2 = odometer counters
D3 = motor information for turning
D4 = motor information for drive straight
D5 = jump to process 4 when required
Figure 4.17: Data flow for software
Process 1:
This is the main section of the program. It runs a tight loop checking for data
from the sensors on port A and also checking the odometer readings to initiate a
compare function to maintain straight line driving.
40
Process 2:
Process 2 is a large subroutine called every time a turn is needed. It accesses data
from port A. It checks sensors and turns relative to their status. After the motors
have been adjusted to gain desired performance the code returns to the main loop,
process 1.
Process 3:
This is an interrupt service routine that determines which odometer sensor has
triggered and increments the respective counter. The counter is a byte stored in
memory and is cleared regularly to avoid overflow issues.
Process 4:
This process is a subroutine used to maintain straight line driving. It is called
from the main program loop and works by comparing the odometer counters and
adjusting motor speeds to maintain a constant even speed between the motors.
This results in even wheel speed hence straight driving.
The above set-out of structure and processes has allowed the following code to be
written and implemented into the Mobile Manoeuvring Robot. The next sections will
break the code down into segments and subroutines and detail the operation of each
function. From this, the code can be easily understood and modified to suit similar
purposes. A full code listing is available in Appendix B.
4.6.1 Address Definition
“ ;ADDRESS DEFINITION
PORTA
equ $00
;Port A Data
PORTB
equ $01
;Port B Data
DDRA
equ $02
;Port A Data Direction
…
…
…
ADR16L
equ $1FD ;
ADR17H
equ $1FE ;
ADR17L
equ $1FF ;
……..”
41
This section of code is simply written to show and name all of the available addresses of
ports etc inside the Motorola HC12. Credit for this section of code goes to Mr Terry
Byrnes. The rest of the program then references these address names for ease of
reading, understanding and debugging. For instance the code to output hexadecimal 10
would be
MOVB #$10, PORTA
This is much easier to understand than a code that says
MOVB #10, $00
Without knowing the addresses of every single port it would be near impossible to
decipher the assembly language code.
4.6.2 Variable Definition
The next step in the code is variable definition. This simply defines all of the variables
that will be used throughout the program and defines a location for their storage in
memory. The variables start at address $0200 and list onwards from this address.
;*************VARIABLE DEFINITION***********************************
ORG $0200
START DEFINITION AT ADDRESS $0200
ODMA
DC.B
0
ODMB
DC.B
0
COUNT
DC.B
0
;DEFINE VARIABLES
4.6.3 Main Program
After variable definition is the main program control loop. This section is responsible
for initialising all of the hardware and ports. The bottom tight loop is responsible for
ensuring the robot drives straight and also that the sensors are checked frequently for
object detection.
;**************MAIN PROGRAM..CONTROL LOOP************************
;NOTE: NO ACTION WILL OCCUR UNTIL THE IRQ INTERRUPT IS ACTIVATED UNLESS
FRONT SENSOR IS TRIGGERED
MAIN
ORG
$0400
;START PROGRAM STORE AT $0400
LDS
#$0700
;SET STACK POINTER
42
CLR
COPCTL
;DISABLE COMPUTER OPERATING
NORMALLY WATCHDOG
JSR
INITSC0
;INITIALISE SERIAL PORT
JSR
INITKWG
;INITIALISE PORT G
JSR
INITPWM
;SET UP PULSE WIDTH MODULATION ON
PORT P
WAIT
JSR
INITIRQ
;INITIALISE IRQ INTERRUPT
JSR
INITPA
BRCLR
PORTA,$01,SKP
;CHECK FRONT SENSOR AND IF ON
BRANCH TO TURNL
SKP
JSR
TURNL
LDAA
COUNT
CMPA
#$5A
;HAS MOTOR A COUNTED xx TIMES YET
(xx/2 REVOLUTIONS)
BMI
WAIT
;IF NOT ,WAIT AND CHECK AGAIN
JSR
COMP
;IF SO JUMP TO COMP (compare function)
BRA
WAIT
;AFTER COMP GO BACK AND WAIT FOR
ANOTHER xx/2 REVOLUTIONS
The main loop code runs indefinitely until the reset button on the microcontroller is
pressed or the power source is interrupted. Firstly it checks port A to determine
whether the front sensor is triggered.
If port A shows the front sensor has been
triggered the program branches out of the main loop to the turn left subroutine. This
subroutine will be explained further on. If the sensor does not show to be triggered the
main loop continues on to check how many times it has been since the odometer was
serviced. It does this by loading the number of revolutions motor A has turned and
comparing it with a set number, currently $5A. This number can be adjusted to alter the
performance of the robot. If motor A has not turned $5A counts, the main program
branches back to the start of the loop and continues checking the sensor followed by the
odometer counters. Once motor A has turned $5A counts, the main loop branches to the
subroutine ‘COMP’ which compares motor A counts with motor B counts and adjusts
the motor speeds accordingly to achieve straight line driving. This subroutine will also
be detailed later.
4.6.4 DRFWD Drive Forward Subroutine
This subroutine is very basic and is called in order to start the robot in a forwards
motion. Bytes relative to the desired speed are moved into the PWDTY address that
43
applies to the motor to be run. The byte moved is between $00 and $FF and is the
percentage high time of the duty cycle of the pulse used to control the speed. A value of
$FF will be full time on, hence maximum speed, and $00 will be full time low, hence
not moving at all. The value $A0 has been chosen from physical observation to define
the desired speed as smooth but reasonable pace.
*************DRIVE FORWARDS*********************************************
DRFWD MOVB
#$A0, PWDTY0
;DUTY CYCLE FOR CHANNEL 0|
MOVB
#$A0, PWDTY2
;DUTY CYCLE FOR CHANNEL 2| **DRIVE
FORWARDS
RTS
;RETURN FROM SUBROUTINE
4.6.5 Turning subroutines
The subroutines used to turn in either the left or right direction are very similar and
hence only one subroutine will be detailed. The TURNL code is explained in the
following.
Before the robot will turn left, several sensors are checked to ensure the turn signal was
not generated by noise and also to ensure there are no objects in the direction of turn.
Firstly the front sensor is checked repeatedly to ensure it is definitely set and that the
signal was not generated by noise. This is done by loading a number into index register
X and then looping that number of times, checking the sensor and decrementing X each
loop. If at any time the sensor does not read triggered, the instruction to turn left will be
aborted and the program will return to the main loop. Once the loop has been executed
X times and is guaranteed to be a legitimate turn request, the left sensor is checked to
ensure there is room to turn. If the left sensor is clear the code proceeds with a left turn.
If not clear the code branches to the turn right subroutine.
In order to turn left, a duty cycle value is written to the left wheel PWDTY register in
order to turn it backwards. The odometer for motor A is cleared and watched in a tight
loop until it reaches the specified number of turns relative to a right angle turn. Running
the motors from an 11V power supply proved decimal 90 counts to be a 90 degree turn.
This takes into account the wind down time of the motor (the inertia continues the
wheel turning for a small time after voltage is turned off). Once the robot has come to a
halt after turning, it continues on a forward path. Between all of the direction changing
44
commands a delay is implemented to reduce some of the jerky motion. The delay
subroutine is used to create this delay.
;********TURNING CODES******************************************************
TURNL
LDX
#$0A00
LP
BRCLR
PORTA,$01,FALSE
DEX
;|
;LOOP TO CHECK SENSOR $0A00 TIMES
TO ENSURE NOT JUST NOISE
SKR
CONTL
BNE
LP
;|
BRCLR
PORTA,$04,SKR
;IF LEFT SENSOR(3) BLOCKED, TURN
JSR
TURNR
;RIGHT INSTEAD
LDAA
#'L'
JSR
TXBYTE
MOVB
#$00,PWDTY0
;|
MOVB
#$00,PWDTY2
;|STOP MOTORS
JSR
DELAY
;WAIT FOR DELAY PERIOD
MOVB
#$00,ODMA
;|
MOVB
#$00,ODMB
;|CLEAR ODOM COUNTERS
MOVB
#$80,PWDTY1
;TURN MOTOR B BACKWARDS
LDAA
#$00
LDAB
ODMB
CPD
#90
;SET NUMBER RELATIVE TO A 90 DEGREE
TURN
FALSE
BLT
CONTL
MOVB
#$00,PWDTY1
JSR
DELAY
JSR
DRFWD
;WAIT FOR TURN TO COMPLETE
;CONTINUE FORWARDS
RTS
;RETURN FROM SUBROUTINE
The backup subroutine is called only after the code has deemed it impossible to move
forward or turn in either direction. The code is designed to only reverse long enough to
clear one side of the robot and allow it to turn in that direction.
Initially it ensures both motors are stopped, and then turns both wheels backwards at the
same speed as it normally drives forward. The code then drops into a loop which waits
for either side sensor to clear. First it checks the left sensor and turns left then exits the
loop if clear; followed by the right sensor and turns right and exits if it is clear. If
neither is clear then the loop continues until either one of the directions is vacant. After
45
the robot has turned in either direction the backup subroutine is exited and the main
loop continues.
BACKUP ;LDAA
WFCLR
#'K'
;SEND K THROUGH SERIAL PORT
;JSR
TXBYTE
;(DEBUG)
;MOVB
#$00,PWDTY0
;|
;MOVB
#$00,PWDTY2
;|STOP MOTORS (DRIVING FORWARDS)
;JSR
DELAY
;WAIT DELAY PERIOD
;MOVB
#$A0,PWDTY1
;|
;MOVB
#$A0,PWDTY3
;|REVERSE STRAIGHT
BRCLR
PORTA,$02,OUTL
;IF LEFT NOT SET BRA TO OUTL
;BRCLR
PORTA,$04,OUTR
;IF RIGHT NOT SET BRA TO OUTR
BRA
WFCLR
;IF L&R SET, BRA WFCLR. WAIT FOR L OR
R TO CLEAR
OUTL
JSR
TURNL
;TURN L WHEN L SENSOR IS CLEAR
OUTR
JSR
TURNR
;TURN R WHEN R SENSOR IS CLEAR
JSR
DELAY
RTS
;RETURN TO MAIN LOOP
4.6.6 Delay
The delay code works with a loop inside a loop decrementing a value slowly. The inner
loop increments index register X by one for every loop, until it ‘rolls over’ from $FFFF
to $0000. When index register X reaches zero, the outer loop value (stored in index
register Y) decrements by one. Thus, the delay is the time it takes to increment X
$FFFF times, multiplied by the number initially stored into index register Y. To adjust
the delay time it is easiest to adjust the initial value in index register Y.
;*************DELAY*******************************************************
;CODE TO ADD A DELAY TO EASE THE SWITCHING OF MOTORS
;GIVES APPROX 2 SEC DELAY. CAN SHORTEN TIME BY INCREASING INITIAL Y
VALUE
DELAY LDY
#$FFDC
;INITIAL VALUE FOR Y
DELA LDX
#$0000
;INITIAL CONDITION OF X
DEL
INX
BNE
;INCREMENT X BY 1
DEL
;IF Z NOT = 0 BRANCH TO DELAY
INY
BNE
DELA
RTS
46
4.6.7 COMP Compare Subroutine
The entire purpose of the COMP subroutine is to compare the speeds of each motor and
ensure they run in parallel. This ensures straight line driving which was one of the
major project guidelines. This function is called by the main loop every time the
odometer for motor A reaches its defined value. When this occurs, it writes a new line
through the serial port then compares ODMA (odometer of motor A) with ODMB
(odometer of motor B). If ODMA is larger than ODMB then motor A is spinning too
fast, therefore the subroutine branches to the label ‘A2FAST’ where the motor speeds
are adjusted. Likewise if ODMB is larger than ODMA the subroutine branches to the
label ‘B2FAST’.
A2FAST works on a simple rule. Before simply reducing the duty cycle in the PWDTY
register it is necessary to check whether that duty cycle is above a certain threshold.
Without this check, the robot would eventually slow to a stop. If the duty cycle is lower
than this threshold, in this case $65, instead of slowing Motor A it will instead increase
the speed of motor B slightly. Likewise the routine B2FAST works on the same
threshold, if the duty cycle drops below the threshold, it will speed motor A instead of
slowing motor B. Of course if the duty cycle is above the threshold it will simply
reduce the speed of the respective motor.
;*************COMPARE SPEEDS********************************************
;CODE TO COMPARE MOTOR A AND B SPEEDS AND CONTROL H BRIDGE
COMP JSR
NEWLINE
;START NEW LINE ON SERIAL PORT
LDAA
ODMA
;LOAD MOTOR A COUNT INTO ACC A
CMPA
ODMB
;COMPARE MOTOR A WITH MOTOR B
BPL
A2FAST
;IF MOTOR A FASTER THAN MOTOR B
BMI
B2FAST
:IF MOTOR A SLOWER THAN MOTOR B
;------------------------------------A2FAST JSR
NEWLINE
;CASE MOTOR A IS FASTER THAN B
LDAA
#'a'
JSR
TXBYTE
;TX BYTE THROUGH SERIAL (DEBUG)
LDAA
PWDTY2
;LDAA SPEED OF MOTOR A
CMPA
#$65
BMI
FASTB
;IF MOTOR A IS SLOWER THAN $65
;SPEED UP MOTOR B
47
SUBA
#$01
STAA
PWDTY2
;SLOW MOTOR A SLIGHTLY
BRA
DONE
;EXIT
PWDTY0
;|
ADDA
#$01
;|SPEED B UP ONE
STAA
PWDTY0
;|
BRA
DONE
FASTB LDAA
;IF MOTOR A IS FASTER THAN $C5
;-------------------------------------B2FAST JSR
NEWLINE
;CASE MOTOR B IS FASTER THAN A
LDAA
#'b'
JSR
TXBYTE
;TX BYTE THROUGH SERIAL (DEBUG)
LDAA
PWDTY0
;LDAA WITH SPEED OF MOTOR B
CMPA
#$65
;|
BMI
FASTA
; | IF MOTOR B GOING TOO SLOW, SPD UP
A
SUBA
#$01
;|
STAA
PWDTY0
;|SLOW MOTOR B SLIGHTLY
BRA
DONE
FASTA LDAA
PWDTY2
;|
ADDA
#$01
;| SPEED A UP BY ONE
STAA
PWDTY2
;|
#$00, COUNT
;|
MOVB
#$00, ODMA
;| CLEAR COUNTERS
MOVB
#$00, ODMB
;|
DONE MOVB
RTS
;RETURN AND WAIT FOR NEXT COMPARE
4.6.8 KWGISR Key Wake Up Port G
This is the code written for the interrupt service routine which is responsible for
incrementing the odometer counters every time the microcontroller receives a signal
from the odometer sensors. Basically, when the interrupt port is triggered by a falling
edge on any port G pin (5v down to 0v), the code checks each connected pin (pins 0 and
1) to determine which sensor triggered the interrupt. If pin 0 triggered the interrupt then
it loads ODMA and adds 1, if it was pin 1 that triggered it loads ODMB and increments
it. If both pin 0 and 1 appear to not have triggered the interrupt then the subroutine will
simply exit and the main program will continue to run.
48
;*****************KEY WAKE UP PORT G ***********************
;ADDS 1 TO COUNTER FOR CORRESPONDING MOTOR
;****SENSOR G 0************
KWGISR
BRCLR
KWIFG,$01,NOTG0
;CHECK BIT 0
LDAA
ODMB
;IF MOTOR B, LDA WITH ODOM COUNT B
ADDA
#$01
;ADD 1 TO ODMB COUNT
STAA
ODMB
;STORE BACK TO ODMB
LDAA
#'B'
JSR
TXBYTE
;WRITE TO SERIAL PORT (DEBUG)
;****SENSOR G 1************
NOTG0 BRCLR
KWIFG,$02,NOTG1
;CHECK BIT 1
LDAA
ODMA
;IF MOTOR A, LDA WITH ODOM COUNT A
ADDA
#$01
;ADD 1 TO COUNT
STAA
ODMA
;STORE BACK TO ODMA
LDAA
COUNT
ADDA
#$01
STAA
COUNT
LDAA
#'A'
JSR
TXBYTE
;WRITE TO SERIAL PORT (DEBUG)
;********FALSE INTERRUPT********
NOTG1 MOVB
#%00000011,KWIFG
RTI
;CLEAR WAKE UP FLAGS
;RETURN FROM INTERRUPT
4.6.9 IRQISR IRQ Interrupt Service Routine
This interrupt service routine waits for the falling edge on the IRQ interrupt. This is
input to the microcontroller from a push button switch which is intended to start the
operation of the robot. When the button is pressed, the service routine delays before
branching to the DRFWD subroutine which initiates a forward motion. The delay
provides some software switch bounce as this interrupt is set to be edge sensitive only.
;**********************IRQ SERVICE ROUTINE**************************
;THIS INTERRUPT STARTS THE ROBOT WHEN BUTTON IS PRESSED
IRQISR JSR
JSR
RTI
DELAY
;PROVIDES SOME SWITCH BOUNCE
DRFWD
;BEGIN DRIVING
;RETURN FROM INTERRUPT
49
4.6.10 Initialisation of Ports and Interrupts
There are several different subroutines used to initialise ports and define interrupt
control. One exists for each of the following: Pulse width modulation, port P; Port A;
Key wake up Port G and the serial port.
It is essential that these initialisation
subroutines are run at the start of the program before any actual running commences.
This ensures the interrupts are set ready to work, the serial port is communicating and
that all input and output is taken care of.
The Pulse Width Modulation (PWM) is the method of controlling the speed of the
motors. The Motorola HC12 has four channels devoted to PWM and can easily be set
using the following code. Each of the bytes moved into the PWM control registers
provides a certain setting required for the desired use of the PWM channels. Clear
explanation of each bit can be found in the data sheet for the Motorola HC12. First
specification set is the pre-scaler. This is used to slow down the clock for use as the
PWM. Extremely high frequencies are not desired as they create excess power loss and
heating through the H Bridge switching. Used here is a pre-scaler of 128 which means
the frequency of the PWM will be 128 times smaller than the frequency of the
microcontroller clock. The PWPOL byte takes care of which clock to use for each
channel and also the polarity of the duty cycle for each cycle. PWEN simply enables all
the selected lines to be output regardless of the data direction register. PWCTL sets
port P to have an active pull up device enabled.
;***************************************************************************
;SETUP PWM Channels
INITPWM MOVB
#%00111111,PWCLK ;PRESCALER OF /128
MOVB
#%00001111,PWPOL ;PPOL
MOVB
#%00001111,PWEN
;ENABLE ALL OUTPUTS
MOVB
#%00000010,PWCTL
;PULL UP DEVICE ENABLED
#$FF,PWPER0
;|
MOVB
#$FF,PWPER1
;|PERIOD FOR PWM
MOVB
#$FF,PWPER2
;|
MOVB
#$FF,PWPER3
;|
SETPWM MOVB
50
RTS
;RETURN TO MAIN
Initialisation for port A simply involves setting the three used pins for data input and
setting all of the pins to initially start with logic low. This ensures no sensor readings
take place until the sensor actually detects an object.
***************INITIALISE PORT A********************************************
INITPA MOVB
#%11111000,DDRA
;SET PORT A BITS FOR OUT AND IN 0 =
INPUT
MOVB
#%00000000,PORTA
;ENSURE PORT A INPUTS ARE ZEROES
WAITING FOR ACITVE HIGH
RTS
Initialising port G for key wake up behaviour involves setting conditions in four
separate registers. DDRG sets the data direction for port G, the used pins need to be
data input while the rest can be either. Writing to KWIFG clears the wake up flags on
the desired pins and KWIEG enables the selected pins to be key wake up interrupts.
This means that as soon as the edge is detected the interrupt will automatically service.
The PUCR register is used to enable or in this case disable all of the pull up resistors on
selected ports. As no pull up resistors are desired on any ports in use it is simplest to
write all zeroes to this register. Storing the opcode for the jump command into the
pseudo vector notifies the interrupt what to do when the interrupt is triggered. Also
mentioned here is the address to jump to. This is the interrupt service routine that was
outlined above. It is essential that the interrupt mask bit is cleared after these registers
have been initialised.
**************INITIALISE PORT G FOR KEY WAKE UP***************************
INITKWG MOVB
#%11111100,DDRG
;BITS 0-1 AS INPUT
MOVB
#%00000011,KWIFG
;CLEAR WAKE UP FLAG 0-1
MOVB
#%00000011,KWIEG
;ENABLE KEY WAKE UP INTERRUPTS
MOVB
#%00000000,PUCR
;SET PORT G, H IRQ AND XIRQ FOR PULL
DOWN (DISAHLE ALL PULL UPS(ALL 0'S))
LDAA
#$06
;JMP COMMAND OPCODE
STAA
$07B8
;RTI PSEUDO VECTOR
LDD
#KWGISR
;ADDRESS TO JUMP TO, KWG ISR
STD
$07B9
CLI
;CLEAR INTERUPT MASK
RTS
51
The serial port requires having the baud rate set and also to enable the transmitter. It is
also adequate to enable the transceiver which accomplishes the same task. The baud
rate value is chosen and then a corresponding number is found from the baud rate
generation table in the HC12 data sheet. Loading accumulator A with the contents of
SC0DRL clears the flags inside that register and readies the serial port for use.
;****************SERIAL PORT**********************************************
; TO USE THE SERIAL PORT, SET BAUD RATE TO 19200
; BAUD. THE VALUE HERE IS A 16 BIT DIVISOR.
INITSC0 LDD
#26
; VALUE FROM BAUD RATE GENERATION
TABLE
STD
SC0BDH
LDAA
#$0C
STAA
SC0CR2
LDAA
SC0DRL
; ENABLE TRANSCEIVER
;CLEAR FLAGS
RTS
4.6.11 Serial Port Communications
Two simple subroutines were written for serial port communication. Although not
necessary to the correct functioning of the Mobile Manoeuvring Robots performance,
they provide an excellent debugging facility. Characters can be sent to a computer
screen to understand which parts of code are being run and hence follow the real time
branching and code order.
NEWLINE simply loads the ASCII value of a carriage return and uses the TXBYTE
subroutine to transmit it to the screen. This is followed by an ASCII line feed being
sent in a similar matter. On the computer screen this looks the same as hitting an enter
key in a text editor.
;***************SERIAL PORT WRITING COMMANDS******************************
; SEND A CARRIAGE RETURN AND LINE FEED TO SCREEN
NEWLINE LDAA
JSR
#$0D
;LOAD CARRIAGE RETURN FOR ASCII
TXBYTE
;TRANSMIT TO SCREEN
52
LDAA
#$0A
;LOAD LINE FEED ASCII
JSR
TXBYTE
;TRANSMIT TO SCREEN
RTS
;RETURN
The TXBYTE subroutine checks the serial ports status register to await the clear flag
before sending the data stored in accumulator A through the serial port. It is essential to
await the clear flag before sending data to avoid data contentions.
; TRANSMIT A CHARACTER STORED IN ACCUMULATER A
TXBYTE
STAA
BRCLR
SC0SR1, #$80
;WAIT FOR CLEAR FLAG
SC0DRL
;SEND DATA THROUGH SERIAL PORT
RTS
;**************************************************************************
53
CHAPTER 5
PERFORMANCE AND DATA ANALYSIS
No specific data was obtained from the results of this dissertation. This is due to the
fact that it is a simple performance based outcome. If GPS tracking or similar had been
used to control direction there would be headings and position plots to consider. The
only way to assess the performance of the Mobile Manoeuvring Robot is to visually
assess the performance.
This performance however can be broken down into the
various aspects of the robot such as mechanical, software, electrical and so on. This
chapter discusses the performance of each individual aspect of design and in some cases
suggests recommendations to overcome some of the poorer performance aspects.
5.1 Sensor performance
The sensors used in the Mobile Manoeuvring Robot ended up working successfully. A
reasonable range was achieved (explained later) and a clean voltage drop was obtained
for communication with the microprocessor. Overall these are the only requirements
necessary for operation of the robot.
To greatly assess the performance of the sensors a simple test was performed to
determine the range of object detection. This involved sensor height range, width range
and distance range. Basically an object was held to the side of the sensors view and
then moved slowly across the sensors view until the response triggered. By lining this
point up to rulers laying in each direction orthogonal to each other (x, y, z axes) a point
was recorded in 3d space. This was performed in every direction until each extremity of
the sensors range was known.
These points can then be plotted using computer
software to give a clear indication of the effective distance of the sensors. The object of
choice was a small white block of timber which gave an effective reflection of light.
The following table of data was obtained from physical experimentation with one of the
sensors.
54
Coordinate
Position
X
Y
Z
1
0
200
0
2
50
180
0
3
-55
180
0
4
0
180
65
5
0
180
-50
6
35
180
35
7
-35
180
-35
8
-35
180
50
9
35
180
50
10
45
180
30
11
-45
180
30
12
45
180
-20
13
-50
180
-20
14
20
180
60
15
-20
180
60
16
20
180
-40
17
-25
180
-40
TABLE 5.1: Sensor range
Using computer software to plot these results shows the range the sensor can detect.
The following MATLAB code was produced to plot these points as vectors from the
origin in three dimensional space.
x = [0 50 -55 0 0 35 -35 -35 35 45 -45 45 -50 20 -20 20 -25];
y = [200 180 180 180 180 180 180 180 180 180 180 180 180 180 180 180 180];
z = [0 0 0 65 -50 -35 -35 50 50 30 30 -20 -25 60 60 -40 -40];
loop = 1;
for loop = 1:17;
plot3([0,x(1,loop)], [0,y(1,loop)], [0,z(1,loop)])
hold on;
loop = loop + 1;
end
plot3([0,x(1,1)], [0,y(1,1)], [0,z(1,1)], 'r')
55
Figure 5.1 shows the MATLAB 3D plot which depicts roughly the boundary an object
must enter to be detected by the sensor. The red line represents the perpendicular
sensing distance and the blue lines show the extremities of the reflected light.
Figure 5.1 Sensor spectrum
This is a practical spread of detectable range. If pointed towards the driving surface the
sensors will detect any object that comes within the driving direction of the robot.
After the large time and effort that went into the design, construction and testing
explained in chapter 4, it has become evident that the price of commercial sensors is
very affordable. If the sensors had been purchased as a whole unit it is presumable that
few troubles would have occurred from the vision aspect for the duration of the project.
This in turn would have allowed a much greater development of the practical side of the
robot. Dead reckoning guidance could have been implemented and a useful purpose
such as object retrieval could have been created. For sensors in similar applications it is
easy to see that it is worth spending extra money and having a small, compact sensor
that can be relied on relatively heavily.
56
5.2 Mechanical performance
The chassis used for the duration of this project served its purpose sufficiently. It was
possible to mount all the required equipment, however room for additional components
is exhausted. The major problem with the chassis design at this point is the lack of
room for a suitable battery. The battery used can sustain operation for only a short
period of time and so either more cells or a new design of battery is required. For this
to take place more room is required on the chassis. Also for extending any operation of
the robot, such as a retrieval arm, would require chassis space to mount and control.
The only successful way to continue work on this project, including extended operation
and achieving smoother running, is to re-design and construct the chassis. A more
successful approach to this than the prototype used would be to construct the chassis in
a series of layers. Each layer would contain a separate part of operation for the robot.
By designing in this manner there is always more room for additional components by
adding additional layers until all objectives have been met. After the robot is successful
to the point of putting into operation it could be finally re-designed into a more compact
unit suitable for practical use or manufacturing. This would encompass such factors as
aesthetics, practicality and weight reduction.
Figure 5.2 below shows the application of the layered board system. The bottom layer
here contains the drive wheels, motors and H Bridges. It may also be practical to mount
the microcontroller here if there is room. Layers are joined by ribbon cables or wires
and are bolted together for rigidity. It is important to consider the spacing of the layers
as if the robot becomes too tall, stability will suffer greatly.
57
Figure 5.2: Layered approach to robot design.
This design allows greatly for troubleshooting as each layer can be pulled apart
separately to give room for soldering, viewing and modifying.
It would also be
advisable to allow a lower layer for the battery storage as they are likely to be one of the
heavier components and mounting them high would affect the robots stability.
5.3 Software Performance
The software as explained above follows a very simple structure. Because of this there
are few errors that affect the performance of the Mobile Manoeuvring Robot. As a
whole, the software completed the overall objective of the project and so should be
recognised as a success.
As a formal test for the straight line driving performance, a pen or chalk can be attached
to the unit to track the trajectory of the robot. To achieve this, a chalk stick was taped to
the rear of the robot. Ideally it should be mounted midway between the drive wheels
however this was not practical for the experiment. The robot was then placed on a clear
and clean slab of concrete and set to run. The result was a line with slight curvature at
the beginning, but as a whole very straight. The slight curvature at the start is due to the
motors starting at full speeds and slowly equalizing. During this time the robot will turn
a slight, hardly noticeable curve. Figure 5.3 shows the testing in progress and figure 5.4
shows the results of the experiment.
58
Figure 5.3: Straight line testing
Approximately 1 metre
Figure 5.4: Results of straight line test
59
Figure 5.4 shows the results of the straight line test.
This section of line is
approximately one metre from the start of the test and approximately one metre long.
The chalk line has been drawn over to make more visible and a string line pulled tight to
lie beside it as a control. It can be seen that as a whole, the robot drives in a very
straight line with only slight variances in either direction. These variances may be due
to the inaccuracies of chalk on concrete or the slight changing in motor speeds and
loads. Either way this test proves the robot to adequately meet the straight line driving
performance objective.
5.4 Overall Performance
As a whole the robots performance is best assessed against the performance guidelines
set out in the project specification. Whether or not improvements can be made, the
performance guidelines are the real assessment criteria of the Mobile Manoeuvring
Robots performance. The robots performance in relation to the initial guidelines is
outlined below in detail.
Performance guideline one:
•
Travel in a straight line when in a clear area with no manual assistance.
The Mobile Manoeuvring Robot encompasses odometer sensors and interrupt control to
achieve straight line driving.
When in a clear area free from objects, the robot
maintains a constant speed and direction. Hence this performance guideline is met
adequately.
Performance guideline two:
•
Stop before colliding with any obstacles that are in the path
Once the robot is in motion, any detectable object is avoided. Issues with this aspect of
performance come into affect with small objects that are missed by the relatively narrow
range of the sensors. Obstacles such as chair legs and tables are adequately avoided and
as it was not defined what size obstacle is necessary to be avoided; the performance in
this sector is adequate. Increased sensor spread and range would however improve this
performance aspect.
60
Performance guideline three:
•
“Decide” which way is more practical to turn and do so.
The robot follows a strict simple decision making process in turning operations. This
operation is detailed in the code section of this dissertation. If there is not room for the
robot to turn in any one direction, the robot will not attempt the turn and reverse until a
clear path is found. This process ensures that the third performance guideline is met
satisfactorily.
Performance guideline four:
•
Continue on its path in a straight line.
Similarly to performance guideline one, the robot will continue on a straight path after
any turn or reverse decision.
The Mobile Manoeuvring Robot adheres to this
performance guideline.
Time permitting:
Due to time constraints and early issues with hardware design, the time permitting
objectives were not completed.
This however, does not hinder the specified
performance of the robot.
5.5 Conclusions
While several aspects of the Mobile Manoeuvring Robot have ample room for
improvement and extension, the overall success of its performance is noteworthy. The
robot adheres to all of the performance guidelines set out in initial project specifications
and performs satisfactorily. Many aspects need improvement such as the purpose for
this technology (e.g. object retrieval) and restructuring the chassis, however this is not
encompassed within the project definition or requirements. The robot performs as such
that it can move throughout an indoor environment whilst avoiding obstacles. This is
the overall project specification and so must be recognised as a success.
61
CHAPTER 6
DEBUGGING MODULE
The Mobile Manoeuvring Robot has been designed and constructed in such a way for
ease of troubleshooting. An example of this is that the software has been written to
output certain characters through the serial port which can be used to gain
understanding of the actual performance of the robot. The following sections are
written to detail the methods of debugging or troubleshooting the robot when
performance is not desirable.
6.1 Microcontroller Not Working
There are two main reasons for the possible case of the microcontroller not turning on,
either a poor power source or a short circuit on the voltage source lines. The orange
LED on the card12 will determine whether the HC12 is working or not. If the orange
LED is not lit, check the polarity and connection of the battery terminals. If these are
connected properly and securely then it is likely to be either a flat battery, faulty voltage
regulator, or a short circuit from any of the loose wires.
Firstly check the battery, it is easiest to either recharge or connect a different battery to
eliminate this problem. The LM7805 voltage regulator requires approximately 7 to 12
volts at the input to ensure correct operation with a 5 volt output. To test the voltage
regulator, a multimeter can be connected to the output leg. Typically this value will
read 5.04 volts when working correctly. If this voltage is degrading slowly then the
battery is flat or faulty. If there is 5 volts present on this track and is not broken away
from the microcontroller then it is highly likely there is a short somewhere on the robot.
Visually checking wires and contacts is the only way to find most shorts.
6.2 Motors Not Turning
If the microcontroller is on and there is no mechanical output from the robot when the
push button is depressed, then it is likely there is no power supplied to the H-Bridges.
This power comes from a separate supply to the microcontroller and should be 10 – 12
volts. It is connected directly to the top and bottom of the H Bridges. Also ensure all
wires are connected securely between the H-Bridges and the microcontroller and also to
the motors. Ensure H-Bridges are not damaged or burnt out however this is unlikely to
62
be the cause of problem. To ensure the push button has worked and been acknowledged
by the microcontroller, connect the serial port to a computer and run a monitor program
such as OC Console. Depress the button; a character ‘Q’ should be displayed on the
screen if it has worked. A small delay follows this character send before power is sent
to the H-Bridges.
6.3 Not Stopping for Objects
The main cause for the robot not stopping at objects is for the sensors to have failed.
The sensors are powered by the same supply as the microcontroller and so should
always be working if the microcontroller is still on. To test the sensors, view the IR
LED through a digital camera. If the LED is on it will glow a purple shade and if not on
it will remain black. Figure 6.1 shows cases of the LED both on and off.
Figure 6.1: showing IR LED status. (Left: LED on // Right: LED off
If the sensors are not working, check the power supply at the LM7805 voltage regulator
on the sensor PCB.
This should behave the same as the regulator for the
microcontroller detailed above. If 5 volts is present and supplied to the PCB, check all
wires and connections.
If the sensors are working check the operation of the receivers. Connect a multimeter to
the left pin of the receiver (Blue wire). This pin should read 5 volts when there is no IR
light present, and close to 0 volts when it receives reflected IR light. If this behaviour
does not occur check all wiring and components.
63
6.4 Not Driving in a Straight Line
If the robot is moving but fails to drive in a straight line it is most likely caused by a
fault in the odometer sensors. To check these, connect the serial port to a computer and
run a monitoring program such as OC Console. Connect a voltage to one of the motors
to make it spin. As the motor spins, either the character ‘A’ or ‘B’ should be repeated
on the screen. (‘A’ for motor A; ‘B’ for motor B). This character is sent to the screen
for every half turn of the motor armature. If these characters are not being sent to the
screen, either the IR LED, receiver or microcontroller interrupt is failing. Check the
voltage coming from the receiver. The receiver output should read 5 volts until the hole
in the motor shaft is aligned, when it should drop to approximately 0 volts. If this is
occurring and the character is still not being written to the screen disconnect the wire
from port G and apply a voltage edge (5 volts down to 0) directly onto the port G pin. If
this does not send a character to the screen the problem lies within the software. Check
the INITKWG and KWGISR subroutines.
6.5 Stopping for Objects but Irregular Behaviour
If the robot is not behaving as explained in any of the above sections, the problem is
most likely within the software. During construction sometimes changing hardware
required different properties in the code. For instance if the source used to drive the
motors was changed from 10 volts up to 12 volts, the number of odometer counts
required for a 90 degree turn was altered slightly. Due to the greater inertia of the motor
spinning faster, the wheel would continue to turn longer after the power was cut.
Generally, all of the driving subroutines can be operated separately. If major debugging
is needed, it is possible to comment out the ‘BACKUP’ and ‘TURNR’ subroutines
along with the branch instruction in ‘TURNL’. This will then make the robot behave
the same for every circumstance. Every time an object is detected the robot will turn
left. Evidently this is impractical however it provides a good base to start adding
additional code without worrying about all of the loops that are involved with the
driving sequence.
The ‘TURNR’ can then be implemented after the turning left
sequence is working correctly, followed by the ‘BACKUP’ subroutine until the
complete driving sequence is functioning correctly.
64
CHAPTER 7
FUTURE WORK
This chapter summarises the future work that may be carried out on the Mobile
Manoeuvring Robot. Future work has been detailed in each individual section such as
chassis design and software; however this chapter aims to provide the possible future
work in a neat summary.
7.1 Hardware
7.1.1 Chassis Design
As described earlier, the current chassis, consisting of an aluminium box section with
two worm drive gearboxes mounted inside, is barely adequate for the desired purpose of
the Mobile Manoeuvring Robot. The design has very limited space with the current
components as it is required to support:
•
Two gearbox drives with motors
•
Two H Bridge cards
•
One microcontroller card
•
Three obstacle sensors
•
Sensor PCB
•
Noise filter
•
Power Supply
For future work to continue, the chassis needs to be extended or re-constructed. The
layered design explained in chapter 5 (performance and data analysis) is deemed the
most adequate.
7.1.2 Sensor Design
The sensors require very little extra work as they are adequate as they are. If the
purpose of this robot is extended to achieve more practical tasks, the sensors may need
to be adjusted to give a wider range. This may be more suitable for detecting smaller or
less obvious obstacles in the path. This extension may be completed by removing the
65
outer of the torch so that the clocked IR light spreads further rather than being
concentrated to a point. Another method would be to add more clocked light LED’s to
transmit a greater quantity of light, and hence objects will reflect more light to the
receiver. This is not deemed an important aspect of future work however may become
important if the robots performance criteria change.
7.1.3 Power Source Design
Currently, the Mobile Manoeuvring Robot has two power sources. One battery powers
the microcontroller and IR sensors, and the other powers the drive motors. The main
purpose of this concept is to eliminate voltage spikes from the drive motors resetting the
microcontroller.
This problem could be overcome however by adding filters
(capacitors) to the power source or the drive motors. For the purposes of the Mobile
Manoeuvring Robot this was not dealt with as the dual power source was not an issue.
For future work it may be desirable to reduce the amount of battery carried on the robot
to lessen the weight and bulkiness of the system.
7.2 Software Design
The structure of the software depends greatly on the desired performance of the Mobile
Manoeuvring Robot. If future work only extends on the base concept there are several
areas where improvement can be made.
•
Ramping functions on the drive motors instead of starting them at full speed.
This will reduce voltage spikes and make the travel of the Robot much
smoother.
•
Dead reckoning guidance. This will give the robot much more objective. If the
robot ‘knows’ its starting position (zero odometer counts) and also a desired
finishing position, it will have a more logical turning sequence, rather than
simply avoiding the obstacles.
66
CHAPTER 8
CONCLUSIONS
As discussed in chapter 5 (Performance and Data Analysis), the performance of the
Mobile Manoeuvring Robot was a success. All of the performance guidelines were met
including:
•
Travel in a straight line when in a clear area with no manual assistance.
•
Stop before colliding with any obstacles that are in the path
•
“Decide” which way is more practical to turn and do so.
•
Continue on its path in a straight line.
All of these criteria are met satisfactorily however there is room for improvement in
several areas as also explained in chapter 5. Before implementation into any practical
situation the following factors need improvement.
•
Chassis re-design to allow more components e.g. batteries, robotic arms.
•
Software improvements depending on the desired task.
Although unlikely to be the entire solution to any problem, the code and hardware
associated with the Mobile Manoeuvring Robot would provide a good base or inner
structure into many autonomous applications. Depending on the application, it may
require minor or major adjustments to the software to suit. For example an autonomous
vacuum cleaner may use this software, but turn 180 degrees and offset every time an
obstacle is detected, instead of simply turning 90 degrees. This would require only
several extra lines of code.
67
Figure 8.1: Working Prototype of Mobile Manoeuvring Robot
Figure 8.1 shows the prototype robot to date without the power supplies attached.
Overall, the Mobile Manoeuvring Robot was a success in every aspect of performance
however would need substantial work to implement into a practical application.
68
APPENDICES
Appendix A – Project Specification
Appendix B – Software Listing
Appendix C – Software Design Procedure
Appendix D – Component Data Sheets
69
Appendix A – Project Specification
University of Southern Queensland
FACULTY OF ENGINEERING AND SURVEYING
ENG4111/4112 Research Project
PROJECT SPECIFICATION
FOR:
MATTHEW FREE
TOPIC:
Mobil Manoeuvring Robot
SUPERVISOR:
Mark Phythian
ENROLMENT:
BEng (Mtr)
ENG4111 – S1, ONC, 2006
ENG4112 – S2, ONC, 2006
PROJECT AIM:
This project aims to explore the use of sensors and Mechatronic
technology in order to produce an obstacle avoiding robot based on
a household sized application.
PROGRAMME:
Issue A, 17th March 2006
1. Research the background behind mobile technology including motor driven
wheels, microcontrollers and sensors.
2. Analyse different technologies such as sensors and microcontrollers to obtain
the most practical configuration of a mobile system.
3. Design and create prototypes of the mechanical structure of the robot. Analyse
and construct leading design.
4. Write code to define robot manoeuvring/instructions and obstacle identification
and attempted avoidance.
5. Implement paramount designs into final robot.
If time permits
6. Develop a motorized arm to retrieve items.
AGREED:
Student:
_______________________
___/___/___
Supervisor: _______________________
70
___/___/___
Appendix B – Software Listing
This is the code stored in the Motorola HC12 ‘s memory which is executed on the event
of the ‘start’ push button.
;ADDRESS DEFINITION
PORTA
equ $00
;Port A Data
PORTB
equ $01
;Port B Data
DDRA
equ $02
;Port A Data Direction
DDRB
equ $03
;Port B Data Direction
PORTE
equ $08
;Port E Data
DDRE
equ $09
;Port E Data Direction
PEAR
equ $0A
;Port E Assigment
MODE
equ $0B
;Mode
PUCR
equ $0C
;Pull Up Control
RDRIV
equ $0D
;Reduced Drive
INITRM
equ $10
;RAM Position
INITRG
equ $11
;Register Position
INITEE
equ $12
;EEPROM Position
MISC
equ $13
RTICTL
equ $14
;Real Time Interrupt Control
RTIFLG
equ $15
;Real Time Interrupt Flag
COPCTL
equ $16
;COP Control
COPRST
equ $17
;Arm/Reset COP Timer
INTCR
equ $1E
;Interrupt Control
HPRIO
equ $1F
;Highest Priority Interrupt
BRKCT0
equ $20
;
BRKCT1
equ $21
;
BRKAH
equ $22
;
BRKAL
equ $23
;
BRKDH
equ $24
;
BRKDL
equ $25
;
PORTG
equ $28
;Port G Data
PORTH
equ $29
;Port H Data
DDRG
equ $2A
;Port G Data Direction
DDRH
equ $2B
;Port H Data Direction
KWIEG
equ $2C
;
KWIEH
equ $2D
;
KWIFG
equ $2E
;
KWIFH
equ $2F
;
SYNR
equ $38
;
71
REFDV
equ $39
;
PLLFLG
equ $3B
;
PLLCR
equ $3C
;
CLKSEL
equ $3D
;
SLOW
equ $3E
;
PWCLK
equ $40
;
PWPOL
equ $41
;
PWEN
equ $42
;
PWPRES
equ $43
;
PWSCAL0
equ $44
;
PWSCNT0
equ $45
;
PWSCAL1
equ $46
;
PWSCNT1
equ $47
;
PWCNT0
equ $48
;
PWCNT1
equ $49
;
PWCNT2
equ $4A
;
PWCNT3
equ $4B
;
PWPER0
equ $4C
;
PWPER1
equ $4D
;
PWPER2
equ $4E
;
PWPER3
equ $4F
;
PWDTY0
equ $50
;
PWDTY1
equ $51
;
PWDTY2
equ $52
;
PWDTY3
equ $53
;
PWCTL
equ $54
;
PWTST
equ $55
;
PORTP
equ $56
;
DDRP
equ $57
;
ATD0CTL0
equ $60 ;Reserved
ATD0CTL1
equ $61 ;Reserved
ATD0CTL2
equ $62
;ATD Control 2
ATD0CTL3
equ $63
;ATD Control 3
ATD0CTL4
equ $64
;ATD Control 4
ATD0CTL5
equ $65
;ATD Control 5
ATD0STAT0
equ $66 ;ATD Status
ATD0STAT1
equ $67 ;ATD Status Low Byte
ATD0TESTH
equ $68 ;ATD Test
ATD0TESTL
equ $69 ;ATD Test Low Byte
PORTAD0
equ $6F ;Port AD Data Input
72
ADR00H
equ $70 ;A/D Converter Result0
ADR00L
equ $71 ;
ADR01H
equ $72 ;A/D Converter Result 1
ADR01L
equ $73 ;
ADR02H
equ $74 ;A/D Converter Result 2
ADR02L
equ $75 ;
ADR03H
equ $76 ;A/D Converter Result 3
ADR03L
equ $77 ;
ADR04H
equ $78 ;A/D Converter Result 4
ADR04L
equ $79 ;
ADR05H
equ $7A ;A/D Converter Result 5
ADR05L
equ $7B ;
ADR06H
equ $7C ;A/D Converter Result 6
ADR06L
equ $7D ;
ADR07H
equ $7E ;A/D Converter Result 7
ADR07L
equ $7F ;
TIOS
equ $80 ;Timer Input Capture/Output Compare Select
CFORC
equ $81
;Timer Compare Force
OC7M
equ $82
;Output Compare 7 Mask
OC7D
equ $83
;Output Compare 7 Data
TCNT
equ $84
;Timer Counter
TCNTL
equ $85
;Timer Counter Low Byte
TSCR
equ $86
;Timer System Control
TQCR
equ $87
;Reserved
TCTL1
equ $88
;Timer Control 1
TCTL2
equ $89
;Timer Control 2
TCTL3
equ $8A
;Timer Control 3
TCTL4
equ $8B
;Timer Control 4
TMSK1
equ $8C
;Timer Interrupt Mask 1
TMSK2
equ $8D
;Timer Interrupt Mask 2
TFLG1
equ $8E
;Timer Interrupt Flag 1
TFLG2
equ $8F
;Timer Interrupt Flag 2
TC0
equ $90
;TIC/TOC 0
TC0LOW
equ $91
;TIC/TOC 0 Low Byte
TC1
equ $92
;TIC/TOC 1
TC1LOW
equ $93
;TIC/TOC 1 Low Byte
TC2
equ $94
;TIC/TOC 2
TC2LOW
equ $95
;TIC/TOC 2 Low Byte
TC3
equ $96
;TIC/TOC 3
TC3LOW
equ $97
;TIC/TOC 3 Low
73
TC4
equ $98
;TIC/TOC 4
TC4LOW
equ $99
;TIC/TOC 4 Low Byte
TC5
equ $9A
;TIC/TOC 5
TC5LOW
equ $9B
;TIC/TOC 5 Low Byte
TC6
equ $9C
;TIC/TOC 6
TC6LOW
equ $9D
;TIC/TOC 6 Low Byte
TC7
equ $9E
;TIC/TOC 7
TC7LOW
equ $9F
;TIC/TOC 7 Low Byte
PACTL
equ $A0
;Pulse Accumulator Control
PAFLG
equ $A1
;Pulse Accumulator Flag
PACN3
equ $A2
;Pulse Accumulator Count
PACN2
equ $A3
;
PACN1
equ $A4
;
PACN0
equ $A5
;
MCCTL
equ $A6
;
MCFLG
equ $A7
;
ICPACR
equ $A8
;
DLYCT
equ $A9
;
ICOVW
equ $AA
;
ICSYS
equ $AB
;
TIMTST
equ $AD
;Timer Test
PORTT
equ $AE
;Timer Port T Data
DDRT
equ $AF
;Timer Port T Data Direction
PBCTL
equ $B0
;
PBFLG
equ $B1
;
PA3H
equ $B2
;
PA2H
equ $B3
;
PA1H
equ $B4
;
PA0H
equ $B5
;
MCCNTH
equ $B6
;
MCCNTL
equ $B7
;
TC0H
equ $B8
;
TC0HLOW
equ $B9
;
TC1H
equ $BA
;
TC1HLOW
equ $BB
;
TC2H
equ $BC
;
TC2HLOW
equ $BD
;
TC3H
equ $BE
;
TC3HLOW
equ $BF
;
SC0BDH
equ $C0
;SCI 0 Baud Rate
74
SC0BDL
equ $C1
;SCI 0 Baud Rate Low Byte
SC0CR1
equ $C2
;SCI 0 Control 1
SC0CR2
equ $C3
;SCI 0 Control 2
SC0SR1
equ $C4
;SCI 0 Status 1
SC0SR2
equ $C5
;SCI 0 Status 2
SC0DRH
equ $C6
;SCI 0 Data
SC0DRL
equ $C7
;SCI 0 Data Low Byte
SC1BDH
equ $C8
;SCI 1 Baud Rate
SC1BDL
equ $C9
;SCI 1 Baud Rate Low Byte
SC1CR1
equ $CA
;SCI 1 Control 1
SC1CR2
equ $CB
;SCI 1 Control 2
SC1SR1
equ $CC
;SCI 1 Status 1
SC1SR2
equ $CD
;SCI 1 Status 2
SC1DRH
equ $CE
;SCI 1 Data
SC1DRL
equ $CF
;SCI 1 Data Low Byte
SP0CR1
equ $D0
;SPI 0 Control 1
SP0CR2
equ $D1
;SPI 0 Control 2
SP0BR
equ $D2
;SPI 0 Baud Rate
SP0SR
equ $D3
;SPI 0 Status
SP0DR
equ $D5
;SPI 0 Data
PORTS
equ $D6
;Port S Data
DDRS
equ $D7
;Port S Data Direction
PURDS
equ $D9
;
EEMCR
equ $F0
;EEPROM Module Configuration
EEPROT
equ $F1
;EEPROM Block Protect
EEPROG
equ $F3
;EEPROM Control
FEE32LCK
equ $F4
;
FEE32MCR
equ $F5
;
FEETST
equ $F6
;
FEE32CTL
equ $F7
;
FEE28LCK
equ $F8
;
FEE28MCR
equ $F9
;
FEETST1
equ $FA
FEE28CTL
equ $FB
CMCR0
equ $100 ;
CMCR1
equ $101 ;
CBTR0
equ $102 ;
CBTR1
equ $103 ;
CRFLG
equ $104 ;
CRIER
equ $105 ;
;
;
75
CTFLG
equ $106 ;
CTCR
equ $107 ;
CIDAC
equ $108 ;
CRXERR
equ $10E ;
CTXERR
equ $10F ;
CIDAR0
equ $110 ;
CIDAR1
equ $111 ;
CIDAR2
equ $112 ;
CIDAR3
equ $113 ;
CICMR0
equ $114 ;
CIDMR1
equ $115 ;
CIDMR2
equ $116 ;
CIDMR3
equ $117 ;
CIDAR4
equ $118 ;
CIDAR5
equ $119 ;
CIDAR6
equ $11A ;
CIDAR7
equ $11B ;
CIDMR4
equ $11C ;
CIDMR5
equ $11D ;
CIDMR6
equ $11E ;
CIDMR7
equ $11F ;
PCTLCAN
equ $13D ;
PORTCAN
equ $13E ;
DDRCAN
equ $13F ;
RxFG
equ $140 ;
Tx0
equ $150 ;
Tx1
equ $160 ;
Tx2
equ $170 ;
ATD1CTL0
equ $1E0
;
ATD1CTL1
equ $1E1
;
ATD1CTL2
equ $1E2
;
ATD1CTL3
equ $1E3
;
ATD1CTL4
equ $1E4
;
ATD1CTL5
equ $1E5
;
ATD1STAT0
equ $1E6
;
ATD1STAT1
equ $1E7
;
ATD1TESTH
equ $1E8
;
ATD1TESTL
equ $1E9 ;
PORTAD1
equ $1EF ;
ADR10H
equ $1F0
;
76
ADR10L
equ $1F1
;
ADR11H
equ $1F2
;
ADR11L
equ $1F3
;
ADR12H
equ $1F4
;
ADR12L
equ $1F5
;
ADR13H
equ $1F6
;
ADR13L
equ $1F7
;
ADR14H
equ $1F8
;
ADR14L
equ $1F9
;
ADR15H
equ $1FA
;
ADR15L
equ $1FB ;
ADR16H
equ $1FC ;
ADR16L
equ $1FD
ADR17H
equ $1FE ;
ADR17L
equ $1FF ;
;
;*********************************************************************
;MOTOR DIRECTION CONTROL
;pwm channel 0 = motor B CLOCKWISE
;pwn channel 1 = motor B ANTI CLOCKWISE
;pwm channel 2 = motor A ANTI CLOCKWISE
;pwm channel 3 = motor A CLOCKWISE
;*************VARIABLE DEFINITION***********************************
ORG $0200
START DEFINITION AT ADDRESS $0200
ODMA
DC.B
0
ODMB
DC.B
0
COUNT
DC.B
0
;DEFINE VARIABLES
;**************MAIN PROGRAM..CONTROL LOOP************************
;NOTE: NO ACTION WILL OCCUR UNTIL THE IRQ INTERRUPT IS ACTIVATED UNLESS
FRONT SENSOR IS TRIGGERED
MAIN
ORG
$0400
;START PROGRAM STORE AT $0400
LDS
#$0700
;SET STACK POINTER
CLR
COPCTL
;DISABLE COMPUTER OPERATING
NORMALLY WATCHDOG
77
JSR
INITSC0
;INITIALISE SERIAL PORT
JSR
INITKWG
;INITIALISE PORT G
JSR
INITPWM
;SET UP PULSE WIDTH MODULATION
ON PORT P
WAIT
JSR
INITIRQ
JSR
INITPA
BRCLR
PORTA,$01,SKP
;INITIALISE IRQ INTERRUPT
;CHECK FRONT SENSOR AND IF ON
BRANCH TO TURNL
SKP
JSR
TURNL
LDAA
COUNT
CMPA
#$5A
;HAS MOTOR A COUNTED xx TIMES YET
(xx/2 REVOLUTIONS)
BMI
WAIT
;IF NOT ,WAIT AND CHECK AGAIN
JSR
COMP
;IF SO JUMP TO COMP (compare function)
BRA
WAIT
;AFTER COMP GO BACK AND WAIT FOR
ANOTHER xx/2 REVOLUTIONS
;*************DRIVE FORWARDS****************************************************
DRFWD
MOVB
#$A0, PWDTY0
;DUTY CYCLE FOR CHANNEL 0|
MOVB
#$A0, PWDTY2
;DUTY CYCLE FOR CHANNEL 2| **DRIVE
FORWARDS
RTS
;RETURN FROM SUBROUTINE
;********TURNING CODES**********************************************************
TURNL
LDX
#$0A00
LP
BRCLR
PORTA,$01,FALSE
DEX
;|
;LOOP TO CHECK SENSOR $0A00 TIMES
TO ENSURE NOT JUST NOISE
SKR
BNE
LP
;|
BRCLR
PORTA,$04,SKR
;IF LEFT SENSOR(3) BLOCKED, TURN
JSR
TURNR
;RIGHT INSTEAD
LDAA
#'L'
JSR
TXBYTE
;TRANSMIT L TO SCREEN (DEBUG)
MOVB
#$00,PWDTY0
;|
MOVB
#$00,PWDTY2
;|STOP MOTORS
JSR
DELAY
;WAIT FOR DELAY PERIOD
MOVB
#$00,ODMA
;|
78
CONTL
MOVB
#$00,ODMB
;|CLEAR ODOM COUNTERS
MOVB
#$80,PWDTY1
;TURN MOTOR B BACKWARDS
LDAA
#$00
LDAB
ODMB
CPD
#90
;SET NUMBER RELATIVE TO A 90
DEGREE TURN
FALSE
BLT
CONTL
MOVB
#$00,PWDTY1
JSR
DELAY
JSR
DRFWD
;WAIT FOR TURN TO COMPLETE
;CONTINUE FORWARDS
RTS
;RETURN FROM SUBROUTINE
;------------------------------------TURNR
;BRCLR
PORTA,$02,SKB
;IF RIGHT SENSOR(2) BLOCKED,
BACKUP INSTEAD
JSR
BACKUP
SKB
LDX
#$0A00
LP2
BRCLR
PORTA,$04,FALSE2
;|
DEX
;|
;|LOOP TO CHECK SENSOR(3) $0200
TIMES TO ENSURE NOT JUST NOISE
CONTR
BNE
LP2
;|
LDAA
#'R'
;SEND ‘R’ THROUGH SERIAL PORT
JSR
TXBYTE
;FOR DEBUG PURPOSES
MOVB
#$00,PWDTY0
;|
MOVB
#$00,PWDTY2
;|STOP MOTORS (DRIVING FORWARDS)
MOVB
#$00,ODMA
;|
MOVB
#$00,ODMB
;|CLEAR ODOM COUNTERS
JSR
DELAY
;WAIT FOR DELAY PERIOD
MOVB
#$80,PWDTY3
;TURN MOTOR A BACKWARDS
LDAA
#$00
LDAB
ODMA
CPD
#90
;SET NUMBER RELATIVE TO A 90
DEGREE TURN
FALSE2
BLT
CONTR
;WAIT FOR TURN TO COMPLETE
MOVB
#$00,PWDTY3
JSR
DELAY
;WAIT DELAY PERIOD
JSR
DRFWD
;CONTINUE FORWARDS
RTS
;EXIT AND RETURN FROM SUBROUTINE
;----------------------------------------------------------------------------------BACKUP
;LDAA
#'K'
;SEND K THROUGH SERIAL PORT
79
WFCLR
;JSR
TXBYTE
;(DEBUG)
;MOVB
#$00,PWDTY0
;|
;MOVB
#$00,PWDTY2
;|STOP MOTORS (DRIVING FORWARDS)
;JSR
DELAY
;WAIT DELAY PERIOD
;MOVB
#$A0,PWDTY1
;|
;MOVB
#$A0,PWDTY3
;|REVERSE STRAIGHT
BRCLR
PORTA,$02,OUTL
;IF LEFT NOT SET BRA TO OUTL
;BRCLR
PORTA,$04,OUTR
;IF RIGHT NOT SET BRA TO OUTR
BRA
WFCLR
;IF L&R SET, BRA WFCLR. WAIT FOR L
OR R TO CLEAR
OUTL
JSR
TURNL
;TURN L WHEN L SENSOR IS CLEAR
OUTR
JSR
TURNR
;TURN R WHEN R SENSOR IS CLEAR
JSR
DELAY
RTS
;RETURN TO MAIN LOOP
;*************DELAY*********************************************************
;CODE TO ADD A DELAY TO EASE THE SWITCHING OF MOTORS
;GIVES APPROX 2 SEC DELAY. CAN SHORTEN TIME BY INCREASING INITIAL Y VALUE
DELAY
LDY
#$FFDC
;INITIAL VALUE FOR Y
DELA
LDX
#$0000
;INITIAL CONDITION OF X
DEL
INX
BNE
;INCREMENT X BY 1
DEL
;IF Z NOT = 0 BRANCH TO DELAY
INY
BNE
DELA
RTS
;*************COMPARE SPEEDS**************************************************
;CODE TO COMPARE MOTOR A AND B SPEEDS AND CONTROL H BRIDGE
COMP
JSR
NEWLINE
;START NEW LINE ON SERIAL PORT
LDAA
ODMA
;LOAD MOTOR A COUNT INTO ACC A
CMPA
ODMB
;COMPARE MOTOR A WITH MOTOR B
BPL
A2FAST
;IF MOTOR A FASTER THAN MOTOR B
BMI
B2FAST
:IF MOTOR A SLOWER THAN MOTOR B
JSR
NEWLINE
;CASE MOTOR A IS FASTER THAN B
LDAA
#'a'
JSR
TXBYTE
;------------------------------------A2FAST
;TX BYTE THROUGH SERIAL (DEBUG)
80
FASTB
LDAA
PWDTY2
;LDAA SPEED OF MOTOR A
CMPA
#$65
;IF MOTOR A IS SLOWER THAN $C5
BMI
FASTB
;SPEED UP MOTOR B
SUBA
#$01
;IF MOTOR A IS FASTER THAN $C5
STAA
PWDTY2
;SLOW MOTOR A SLIGHTLY
BRA
DONE
;EXIT
LDAA
PWDTY0
;|
ADDA
#$01
;|SPEED B UP ONE
STAA
PWDTY0
;|
BRA
DONE
;-------------------------------------B2FAST
JSR
NEWLINE
;CASE MOTOR B IS FASTER THAN A
LDAA
#'b'
JSR
TXBYTE
;TX BYTE THROUGH SERIAL (DEBUG)
LDAA
PWDTY0
;LDAA WITH SPEED OF MOTOR B
CMPA
#$65
;|
BMI
FASTA
; | IF MOTOR B GOING TOO SLOW, SPD
UP A
FASTA
DONE
SUBA
#$01
;|
STAA
PWDTY0
;|SLOW MOTOR B SLIGHTLY
BRA
DONE
LDAA
PWDTY2
;|
ADDA
#$01
;| SPEED A UP BY ONE
STAA
PWDTY2
;|
MOVB
#$00, COUNT
;|
MOVB
#$00, ODMA
;| CLEAR COUNTERS
MOVB
#$00, ODMB
;|
RTS
;RETURN AND WAIT FOR NEXT
COMPARE
;*****************KEY WAKE UP PORT G ***************************************
;ADDS 1 TO COUNTER FOR CORRESPONDING MOTOR
;****SENSOR G 0************
KWGISR
BRCLR
KWIFG,$01,NOTG0
;CHECK BIT 0
LDAA
ODMB
;IF MOTOR B, LDA WITH ODOM COUNT
B
ADDA
#$01
;ADD 1 TO ODMB COUNT
STAA
ODMB
;STORE BACK TO ODMB
81
LDAA
#'B'
JSR
TXBYTE
;WRITE TO SERIAL PORT (DEBUG)
;****SENSOR G 1************
NOTG0
BRCLR
KWIFG,$02,NOTG1
LDAA
ODMA
;CHECK BIT 1
;IF MOTOR A, LDA WITH ODOM COUNT
A
ADDA
#$01
;ADD 1 TO COUNT
STAA
ODMA
;STORE BACK TO ODMA
LDAA
COUNT
ADDA
#$01
STAA
COUNT
LDAA
#'A'
JSR
TXBYTE
;WRITE TO SERIAL PORT (DEBUG)
;********FALSE INTERRUPT********
NOTG1
MOVB
#%00000011,KWIFG
RTI
;CLEAR WAKE UP FLAGS
;RETURN FROM INTERRUPT
;**********************IRQ SERVICE ROUTINE**************************
;THIS INTERRUPT STARTS THE ROBOT WHEN BUTTON IS PRESSED
IRQISR
JSR
DELAY
;PROVIDES SOME SWITCH BOUNCE
JSR
DRFWD
;BEGIN DRIVING
RTI
;RETURN FROM INTERRUPT
;******************************************************************************
;SETUP PWM Channels
INITPWM
SETPWM
MOVB
#%00111111,PWCLK ;PRESCALER OF /128
MOVB
#%00001111,PWPOL ;PPOL
MOVB
#%00001111,PWEN
MOVB
#%00000010,PWCTL ;PULL UP DEVICE ENABLED
MOVB
#$FF,PWPER0
;|
MOVB
#$FF,PWPER1
;|PERIOD FOR PWM
MOVB
#$FF,PWPER2
;|
MOVB
#$FF,PWPER3
;|
RTS
;ENABLE ALL OUTPUTS
;RETURN TO MAIN
82
***************INITIALISE PORT A****************************************************
INITPA
MOVB
#%11111000,DDRA
;SET PORT A BITS FOR OUT AND IN 0 =
INPUT
MOVB
#%00000000,PORTA
;ENSURE PORT A INPUTS ARE ZEROES
WAITING FOR ACITVE HIGH
RTS
**************INITIALISE PORT G FOR KEY WAKE UP**********************************
INITKWG
MOVB
#%11111100,DDRG
;BITS 0-4 AS INPUT
MOVB
#%00000011,KWIFG
;CLEAR WAKE UP FLAG 0-4
MOVB
#%00000011,KWIEG ;ENABLE KEY WAKE UP INTERRUPTS
MOVB
#%00000000,PUCR
;SET PORT G, H IRQ AND XIRQ FOR PULL
DOWN (DISAHLE ALL PULL UPS(ALL
0'S))
LDAA
#$06
;JMP COMMAND OPCODE
STAA
$07B8
;RTI PSEUDO VECTOR
LDD
#KWGISR
;ADDRESS TO JUMP TO, KWG ISR
STD
$07B9
CLI
;CLEAR INTERUPT MASK
RTS
;****************SERIAL PORT******************************************************
; TO USE THE SERIAL PORT, SET BAUD RATE TO 19200
; BAUD. THE VALUE HERE IS A 16 BIT DIVISOR.
INITSC0
LDD
#26
; VALUE FROM BAUD RATE
GENERATION TABLE
STD
SC0BDH
LDAA
#$0C
STAA
SC0CR2
LDAA
SC0DRL
; ENABLE TRANSCEIVER
;CLEAR FLAGS
RTS
;***************SERIAL PORT WRITING COMMANDS***********************************
; SEND A CARRIAGE RETURN AND LINE FEED TO SCREEN
NEWLINE
LDAA
#$0D
;LOAD CARRIAGE RETURN FOR ASCII
JSR
TXBYTE
;TRANSMIT TO SCREEN
LDAA
#$0A
;LOAD LINE FEED ASCII
JSR
TXBYTE
;TRANSMIT TO SCREEN
RTS
;RETURN
83
;--------------------------------------------------------; TRANSMIT A CHARACTER STORED IN ACCUMULATER A
TXBYTE
BRCLR
SC0SR1, #$80
;WAIT FOR CLEAR FLAG
STAA
SC0DRL
;SEND DATA THROUGH SERIAL PORT
RTS
;************************************************************************************
84
Appendix C – Software design procedure
MOBILE MANOEUVRING ROBOT SOFTWARE DESIGN
Objectives: To control the mechanical hardware of a two drive-wheel robot in order to
avoid collision with obstacles. The software must be able to control the unit to travel in
a straight line between objects and is based on assembly level language of the Motorola
68HC12 microcontroller.
Obstacle avoiding
While driving do the following:
• Read the odometer sensors and increment odometer counters
o Check odometer counters and adjust speed for straight driving
• Watch obstacle sensors in a tight loop act accordingly when sensors
triggered.
o If left is clear, turn left otherwise turn right

If left and right blocked reverse
• Continue on a straight path
• Output data through serial port for debugging purposes
• Repeat process continuously
User Information:
The code has five sensors that input to the software. Three of these are obstacle
avoidance sensors read in as data through port A and the other two are concerned with
odometer readings read in as interrupts through port G. The program starts at $0400
with data starting at $0200. The stack pointer must be set in a clear location such as
$0700 and the program counter to $0400 to start the procedure.
When run, the program will output through the serial port the status of the odometer
readings and also controls the speed and direction of both motors to achieve the desired
performance. The program loops continuously to give real time control the mechanical
components
85
System Model
The following data flow diagram shows the basic flow of values through the system.
sensors
PORT
A
Obstacle
Process 1
D1
Process 2
D3
D5
sensors
PORT
G
D4
Odometer
readings
Process 3
D2
MOTOR
CONTROL
Process 4
D1 = Signal of which direction to turn
D2 = odometer counters
D3 = motor information for turning
D4 = motor information for drive straight
D5 = jump to process 4 when required
Process 1:
This is the main section of the program. It runs a tight loop checking for data from the
sensors on port A and also checking the odometer readings to initiate a compare
function to maintain straight line driving.
Process 2:
Process 2 is a large subroutine called every time a turn is needed. It accesses data from
port A. It checks sensors and turns relative to the status of them. After the motors have
been adjusted to gain desired performance the code returns to the main loop, process 1.
Process 3:
This is an interrupt service routine that determines which odometer sensor has triggered
and increments the respective counter. The counter is a byte stored in memory and is
cleared regularly to avoid overflow issues.
Process 4:
This process is a subroutine used to maintain straight line driving. It is called from the
main program loop and works by comparing the odometer counters and adjusting motor
speeds to maintain a constant even speed between the motors. This results in even
wheel speed hence straight driving.
86
Software Specification
Execution structures, Pseudocode
MAIN
set the stack pointer in a clear area
Clear computer watchdog
Initialise serial port
Initialise Kew Wake up on port G
Initialise IRQ Interrupt
Initialise port A
Start loop
check sensor for objects
Branch to turn if necessary
Check odometer counters and branch to compare if necessary
Repeat loop.
DRFWD
start both wheels driving forwards
Return to main
TURNL
ensure signal not just noise
if left blocked, jump to turn right
transmit an L through the serial port
Stop the motors
Turn motor B backwards until robot turned 90 degrees
Stop turning
Continue in straight path (jump to DRFWD)
Return to main
TURNR
ensure signal not just noise
if right blocked, jump to backup
transmit an R through the serial port
Stop the motors
Turn motor A backwards until robot turned 90 degrees
Stop turning
Continue in straight path (jump to DRFWD)
Return to main
87
BACKUP
transmit ‘K’ through serial port
Stop the motors
Delay
Turn both motors backwards
Start loop
if left sensor clear, turn left then go forwards again
If right sensor clear, turn right then go forwards again
Repeat loop
Return to main
DELAY
load a large number
Decrement it slowly
Return to main
COMP
new line through serial port
Load accumulator with odometer count A
Compare with odometer count B
If B bigger than A branch to B2FAST
IF A bigger than B branch to A2FAST
A2FAST
write ‘a’ through serial port
Compare motor A speed with a constant
If faster than constant slow it slightly
If slower than constant branch to FASTB
FASTB
Increase motor B slightly
Return to main
B2FAST
write ‘b’ through serial port
Compare motor B speed with a constant
If faster than constant slow it slightly
If slower than constant branch to FASTA
FASTA
Increase motor A slightly
Return to main
88
Software Module Description (Major modules)
Module Name:
MAIN
Purpose:
To run a tight loop continuously monitoring all sensors and
odometer readings.
Called by:
N/A
Calls:
INITSCO, INITKWG, INITPWM, INITIRQ, INITPA, TURNL,
COMP
Validation:
PORT A OBSTACLE SENSORS
Registers used:
A and memory location COUNT
Module Name:
DRFWD
Purpose:
Initialise driving forward
Called by:
IRQISR, TURNL, TURNR
Calls:
N/A
Validation:
N/A
Registers used:
N/A
Module Name:
TURNL and TURNR
Purpose:
To turn the robot in the desired direction by 90 degrees
Called by:
MAIN
Calls:
TXBYTE, DELAY, DRFWD
Validation:
Outputs to PWDTY registers
Registers used:
A, B, and X
Module Name:
BACKUP
Purpose:
Reverse the robot in a straight line
Called by:
TURNR
Calls:
DELAY, TURNR, TURNL
Validation:
outputs to PWDTY registers
Registers used:
A, B, X
89
Module Name:
DELAY
Purpose:
To create a pause in the program.
Called by:
IRQISR, TURNL, TURNR, BACKUP
Calls:
N/A
Validation:
N/A
Registers used:
X and Y
System Implementation
Data dictionary
Constants and variables used in this code are listed below.
- ODMA
odometer counter of motor A
- ODMB
odometer counter of motor B
- COUNT
variable used in compare function
Conversion procedures
The assembly language code has been written in a text editor such as notepad or
MiniIDE and built into a listing file using MiniIDE. Data has been transferred to
the microcontroller using the program OC Console.
Load Map
-
Data is to be loaded at $0200.
-
Program starts at $0400
-
Stack pointer set to clear area at $0700
Conclusions
The system performed adequately to the required specifications.
The software
responded as desired for all sensor inputs including odometer readings. As a result
of the success, the robot is able to drive at a constant speed in a straight line between
obstacles.
The robots performance could be improved by adding additional code in many of
the functions. One such instance is the adding of ramps in the PWDTY registers to
‘ease’ into the desired speed. If dead reckoning guidance is implemented, this code
will require extensive modification.
90
Appendix D – Component Data Sheets
The following data sheets are the main components used in the construction of the
Mobile Manoeuvring Robot. Not all data sheets will be supplied such as the transistor
sheets which are not specific to the purpose of the Mobile Manoeuvring Robot.
The Microcontroller, Motorola MC68HC12 data sheet will not be included as it is far
too extensive for the purpose of listing the data sheets. The MC68HC12 data sheet can
be downloaded from various sources on the internet.
Z 3235 IR LED
The Z3235 IR LED is a Dick Smith Electronics part available at Dick Smith Electronic
stores. This component is used in all of the IR sensors, both clocked and constant light
sources.
91
Z 1955 Buffered Infra Red Receiver System
The Z 1955 Buffered IR Receiver system is a Dick Smith Electronics part available at
Dick Smith Electronic stores. This component is used in the obstacle avoidance IR
sensors to receive the clocked IR light from the transmitter.
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Z 1956 Infrared Receiving Diode
The Z 1955 IR Receiving Diode is a Dick Smith Electronics part available at Dick
Smith Electronic stores. This component is used in the odometer counting sensors to
receive the IR light.
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CARD12
The card 12 sheet is placed here to show the layout of the MC68HC12 microcontroller.
The card 12 is a user friendly PCB which splits the microcontroller’s pins out into the
separate ports and channels. It provides easy access for soldering and can be attached to
any other PCB by the use of two ‘2*25 pin plugs’. The serial port is accessed on the
card 12 ready for connection to a PC.
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Also included in this appendix are the important pages on Interrupt vectors used for the
CARD12.
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REFERENCES
Polymicro 2004, Application Areas and Markets for polymer Micro-Optics, viewed 9
May 2006, POLYMICRO, http://www.polymicro-cc.com/site/pdf/POLYMICROmarkets.pdf
Media Limited SPG 2006, ‘Explosive Ordnance Disposal and Mine Clearance Gallery’,
viewed 9 May 2006, <http://www.army-technology.com>
Electrolux, ‘Welcome to the Electrolux Trilobite’, viewed 9 May 2006,
<http://www.electrolux.com.au/node142.asp>
2002, ‘Appliances of the Future’, Ricoh Journal, viewed 9 May 2006,
http://www.jnd.org/dn.mss/appliances_of_the_fu.html
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<http://www.nada.kth.se/~hic/hic-papers/isrr-01.pdf>
2001, ‘Robo-Rats Electronics’, viewed 10 May 2006,
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‘Project’, Viewed 10 May 2006, http://www.technology.niagarac.on.ca/
students/d/mdelange/index.html
Tunnel D 2004, ‘SmartAvoidT - A Portable, Scalable Object Avoidance Solution for all
Day/Night/Weather/Smoke Environments’, viewed 10 May 2006,
http://www.navysbir.com/04_3/49.htm
Ward K, ‘Learning Mobile Robot Behaviours by Discovering Associations between
Input Vectors and Trajectory Velocities,’ viewed 10 May 2006,
http://www.uow.edu.au/~koren/Papers/AI97.pdf
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Lee F Lin L, ‘Don't Worry, Be Happy,’ viewed 10 May 2006,
http://robots6270.mit.edu/contests/2001/robots/10/www/
Knudsen J 2000, ‘The Straight and Narrow,’ Viewed 10 May 2006,
http://www.oreillynet.com/pub/a/network/2000/05/22/LegoMindstorms.html
Bitsoi H et al 2001, ‘F.U.B.A.R’, viewed 11 July 2006,
www.ee.nmt.edu/~wedeward/EE382/SP01/group3.pdf
McCoy T et al 2004, ‘Infrared Communications Link with Voice and Data’ viewed 19
July 2006, www.home.people.net.au/~tmccoy
Leppard D, 2‘Using B32's Interrupts IRQ and XIRQ’viewed 5 August,
http://www.seattlerobotics.org/encoder/200008/dougl.html
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